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1977

Habitat selection and use by bighorn sheep (Ovis canadensis) on a northwestern Montana winter range

Mark Edward Tilton The University of Montana

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Recommended Citation Tilton, Mark Edward, "Habitat selection and use by bighorn sheep (Ovis canadensis) on a northwestern Montana winter range" (1977). Graduate Student Theses, Dissertations, & Professional Papers. 6509. https://scholarworks.umt.edu/etd/6509

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ON A NORTHWESTERN MONTANA WINTER RANGE

By

Mark E. Tilton

B.S., Huxley College (W.W.S.C.), 1972 j B.S., University of Washington, 1973 >

\ Presented in partial fulfillment of the requirements for the degree of

: Master of Science I I i UNIVERSITY OF MONTANA

1977

Approved by:

Chairman, Board of Examiners

Dean<7 Graduate "^School

Date /

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Tilton, Mark E., M.S., Spring 1977 Wildlife Biology

Habitat Selection and Use by Bighorn Sheep (Ovis canadensis) on a Northwestern Montana Winter Range (121 pp.)

Director: E. Earl Willard ^ LA'* '

Winter habitat selection and use by bighorn sheep were investi­ gated near Thompson Falls in northwestern Montana. Between 1 January and 30 March 197 6, 197 observations of groups of wintering bighorns provided data on group size, herd sex and age charac­ teristics, movements, home range, and habitat selection. Mean group size was 5.6. Lamb : ewe and yearling : ewe ratios were 92:100 and 42:100, respectively. Minimum winter home ranges averaged 320 acre# (130 ha) for adult females and 271 acres (110 ha) for adult males. Wintering bighorn sheep selected against elevations above 4,800 feet (1,463 m), drainage bottoms, upper slopes, areas with a slope steepness of 10-35 percent, east and southeast aspects, areas greater than 0.2 miles (322 m) from steep terrain, closed forests, and the Pseudotsuga menziesii/Physocarpus malvaceus habitat type. Preferences were shown for cliffs, areas with a slope steepness greater than 80 percent, areas within 0.2 miles (322 m) of steep terrain, shrubland-grasslands and open forests, and the rockland-scree habitat type category. Adult ram groups were observed at significantly higher elevations than ewe-juvenile or young ram groups. Wintering bighorn sheep apparently sought out warmer elevations of the mountains. Mean group size was lowest during periods of decreasing barometric pressure. Percentages of grasses and sedges, browse, and forbs in fecal material were 38, 51, and 11, respectively. Forage utilization was greater above 3,800 feet (1,158 m) elevation than below. There was general agreement on the relative use of habitats by bighorn as estimated by fecal group counts and direct observations of wintering animals. Perpetuation of shrubland-grassland and open forest cover types on the winter range as well as a long-term monitoring program involving the systematic collection of data on herd sex and age characteristics, lungworm loads, and forage utilization levels were recommended.

\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ERRATA SHEET for M.S. Thesis by Mark Tilton-- Habitat selection and use by biyhorn sheep on a northwestern Montana winter range

Tables 9.10,11.12.13,14,15

The columns under the heading "Confidence interval on proportion of group observations (90% family confidence coefficient)" should be in the form: .159

The last line on these tables should be: "Pa < confidence interval on Po = Preference; Pa > confidence interval on Po = Avoidance; Pa within confidence interval on Po = H o n e . " This line should be added to the bottom of Table 10.

Table 16 page 75

First CO 1umn should be 2o00 feet < 2800 feet 4Boo feet > 4800 feet .1 miles < .1 miles .41 miles ^ .40 miles 80 percent > 80 percent

Table 9 page 61

First column should be 2800 < 2800 4810 ^ 4810

Tab 1e 11 page 65

First CO 1umn 80 should be > 80

Table 13 page 69

First CO 1umn should be .41 > .41 ( .66 km) (^ .66 km)

Figure 17 page 77

Temperature ( °C) should be Average daily temperature ( ). The title of the graph should be: " Fig. 17. Average daily barometric pressures (top) and average daily temperatures at two elevations (bottom) during the study period."

L i terature c i ted page 120

Shannon, N . H ., R . J. Hudson, V. C. Brink, and W. D. Kitts. 1975. Determinants of spatial distribution of Rocky Mountain bighorn sheep. J. Wildl. Manage. 39(2): 387-401.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

Page

ABSTRACT ...... ii

ACKNOWLEDGEMENTS ...... iii

LIST OF TABLES ......

LIST OF FIGURES ......

CHAPTER

I. INTRODUCTION ...... I

II, DESCRIPTION OF THE STUDY A R E A ...... 8

Selection ...... 8 Location and Ownership ...... 8 Topography and Geology ...... 11 C l i m a t e ...... 12 Vegetation...... % ...... 15 Fire History...... 17 Land Use ...... 19

III. MATERIALS AND METHODS...... 20

Capture and Marking Techniques ...... 20 Temperature and Snow Measurements ...... 21 Observations of Ungulate Distribution ...... 21 Movements and Home R a n g e s ...... 23 Vegetation Analysis ...... 24 Existing Vegetation Description ...... 24 Potential Vegetation Description ...... 26 Determination of Habitat U s e ...... 28 Bedding Site Habitat Analysis ...... 30 Pellet Group Distribution ...... 32 Fecal pH ...... 33 Food H a b i t s ...... 33 Forage Utilization ...... 34 Availability Sample of the Study A r e a ...... 36 Data A n a l y s i s ...... 37

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IV. RESULTS ...... 40

Existing Vegetation ...... 40 Potential Vegetation ...... 40 Trapping...... 48 Group Size and Age-Sex Composition ...... 48 Movements and Home R a n g e ...... 52 Availability Sample of the Study A r e a ...... 52 Habitat Selection and U s e ...... 59 Elevation ...... 59 Topographic position ...... 59 Slope steepness ...... 59 A s p e c t ...... 66 Distance from steep terrain ...... 66 Plant cover t y p e ...... 66 Habitat t y p e ...... 72 Comparison of Habitat Use by Croup Types ...... 72 Barometric Pressure and Temperature ...... 76 Habitat Use Related to Meteorological Conditions . 76 Bedding Site Characterization ...... 79 Fecal pH ...... _ ...... 79 Fecal Croup Counts Related to Site Factors .... 79 Food H a b i t s ...... 83 Forage Utilization ...... 86 Competition...... 86

V. DISCUSSION...... 88

Trapping ...... 88 Croup Size and Age-Sex Composition...... 89 Movements and Home R a n g e...... 90 Availability Sample of the Study A r e a ...... 90 Habitat Selection and U s e ...... 91 Elevation ...... 91 Topographic position ...... 92 Slope steepness ...... 93 A s p e c t ...... 93 Distance to steep terrain ...... 94 Plant cover types...... 95 Forest habitat types ...... 96 Comparison of Habitat Use by Group T y p e ...... 97 Habitat Use Related to Barometric Pressure and Temperature...... 98 Bedding Site Characterization ...... 100 Fecal pH ...... 101 Food H a b i t s ...... 102 Forage Utilization ...... 103

\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Page

Competition...... 105 Fecal Group Counts Related to Site Factors .... 105 Management Implications ...... 107

VI. SUMMARY...... 112

REFERENCES CITED ...... 115

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

This study was financed by the National Rifle Association of

America and the Montana Cooperative Wildlife Research Unit (U.S.

Fish and Wildlife Service, University of Montana, Montana Department

of Fish and Game, and Wildlife Management Institute, cooperating).

The support of the National Rifle Association allowed a more intensive

level of environmental monitoring than would have been otherwise

possible.

I would like to thank ray committee members, Drs. Earl Willard,

Bart o'Gara, and Lee Eddleraan for their time and assistance during

this project. This manuscript benefitted greatly from Dr. Willard's

help in organizing tables and figures and Dr. O'Gara’s critical review.

My wife, Robin, contributed much time, energy, encouragement, and

companionship throughout the study. Only with her efforts during

trapping activities and her support in time of frustration could this

project have been completed.

I thank Gerald Brown, Montana Department of Fish and Game

Department, for his valuable advice throughout the study. Walt Bodie,

Idaho Department of Fish and Game, provided assistance in trapping

operations. Traps were provided by the Idaho and Montana Departments

of Fish and Game.

Jim and Diane Reichel provided me with a friendly place to stay

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. during my many trips to Missoula. Jim also assisted in trapping and

tagging activities.

Tom Klabunde, U.S. Forest Service, reviewed portions of the

manuscript and obtained meteorological records, for which I am

grateful. Gary HaIvorson, U.S. Forest Service, provided aerial

photographs of the study area. The cooperation and assistance of

the U.S. Forest Service personnel of the Plains and Thompson Falls

Ranger Districts, during the study were greatly appreciated.

I thank all of the personnel of the Montana Cooperative Wildlife

Research Unit for their assistance during the project, especially to

"Ginger" Schwarz for her efficient handling of paperwork associated

with the project and Karen Kaley for typing the final draft of the

manuscript.

Dr. Les Marcum advised me concerning datum analysis, and Dr.

Robert Steele provided a barograph for use during the study.

For their assistance and encouragement during various phases of

the project, I would also like to thank Dr. Les Pengelly, Bob Klaver,

Craig and Sally Benton, the D. E. and C. E. Trudgens, Dennis McCrea,

and Bruce Hoagland.

Maurice and Lois Tilton, my father and mother, assisted with map

work and typing of the manuscript. I am also very grateful to them

for my introduction to the outdoors.

Finally, I would like to thank all of my fellow graduate students

at the University of Montana for their encouragement, friendship, and

willingness to share their knowledge.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

Table Page

1. Winter weather data recorded at Thompson Falls, Montana during the study period (1975-1976), a severe winter (1968-1969), and the 30-year period of 1941-1970 16

2. Comparison of the four major plant cover types on the winter r a n g e ...... 41

3. Age, sex, live weight, reproductive status of females, date of capture, and marking system for seven bighorn sheep captured during summer 1975 49

4. Minimum, maximum, and mean group size of bighorn sheep on winter r a n g e ...... 51

5. Sex and age classification of bighorn sheep on winter range ..... 53

6. Activity ranges of marked bighorn sheep during winter as determined by standard diameters .... 54

7. Minimum home ranges of marked bighorn sheep during winter ...... 54

8. Comparison of areas measured with polar planimeter versus areas predicted by random point sample . . . 60

9. Total bighorn sheep use at various elevations compared to availability of those elevations on the winter r a n g e ...... 61

10. Total bighorn sheep use on topographic position categories compared to availability of those categories on the winter range ...... 63

11. Total bighorn sheep use on various categories of slope steepness compared to availability of those categories on the winter range ...... 65

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12. Total bighorn sheep use on various aspects compared to availability of those aspects on the winter r a n g e ...... 67

13. Total bighorn sheep use at various distances from steep terrain compared to availability of areas at those distances on the winter range ...... 69

14. Total bighorn sheep use on various plant cover types compared to availability of those types on the winter r a n g e ...... 70

15. Total bighorn sheep use on various forest habitat types compared to availability of those types on the winter r a n g e ...... 73

16. Comparisons of habitat use by ewe-juvenile, young ram, and adult ram bighorn sheep g r o u p s ...... 75

17. Mean elevation and mean distance to the nearest 15-foot-minimum (4.6 m) cliff of bighorn sheep groups during low, medium, and high barometric pressures ...... 78

18. Comparison of bighorn sheep mean group size during periods of decreasing, relatively stable, and increasing barometric pressure ..... 78

19. Comparison of habitat characteristics associated with day bed sites and night bed s i t e s ...... 80

20. Comparison of winter fecal pH values of bighorn sheep and mule d e e r ...... 81

21. Observed fecal group frequency distributions compared with theoretical Poisson probabilities . . 82

22. Relationships of fecal group locations to various site factors ...... 84

23. Percent relative densities of plant species in bighorn sheep fecal pellets deposited during winter 1975-76 85

24. Estimated average utilization for five forage species on the winter r a n g e ...... 87

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Figure Page

1. Location of study area ...... 9

2. Location of Big Hole Planning Unit, Lolo National Forest (adapted from Anonymous 1976) 10

3. Fire history of the Big Hole Planning Unit, Lolo National Forest (adapted from Anonymous 1976) 18

4. Map of forest habitat types and habitat type complexes occuring on the study area ...... 42

5. Locations of bighorn sheep and mule deer groups observed between 1 January and 30 March 197 6 (numbers indicate multiple observations) . . . 50

6. Minimum winter home ranges of adult males Nos. 415 and 427, measuring 490 acres (198 ha) and 56 acres (23 ha) , respectively...... 55

7. Minimum winter home range of adult female No. 174, measuring 181 acres (73 ha) ...... 56

8. Minimum winter home range of adult female No. 213, measuring 920 acres (372 h a ) ...... 57

9. Minimum winter home range of yearling male No. 31, measuring 717 acres (290 ha) ...... 58

10. Percentages of bighorn sheep group bedding and feeding sites at various elevations . 62

11. Percentages of bighorn sheep group bedding and feeding sites on various topographic positions . . . 64

12. Percentages of bighorn sheep group bedding and feeding sites on various degrees of slope steepness ...... 64

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13. Percentages of bighorn sheep group bedding and feeding sites on various aspects ...... 68

14. Percentages of bighorn sheep group bedding and feeding sites at various distances to steep t e r r a i n ...... 68

15. Percentages of bighorn sheep group bedding and feeding sites in various plant cover types .... 71

16. Percentages of bighorn sheep group bedding and feeding sites on various habitat types ...... 74

17. Barometric pressures (top) and temperatures at two elevations (bottom) during the study period ...... 77

\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. _____ 'I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I

INTRODUCTION

The history of the bighorn sheep population near Thompson Falls

in northwestern Montana parallels that of many other bighorn sheep

concentrations in the western United States. Fur trappers described

sheep as numerous in the area in the 1830's and 1840's (Cox 1831,

Ferris 1873). Shortly after the turn of the century, these sheep were

greatly reduced in numbers and their distribution drastically restricted.

Couey (1950) reported that the Thompson Falls population was restricted

to a small portion of their former range and estimated the population

at 25 sheep in the early 1940's. The decline apparently led to the

complete extinction of the local herd, as no bighorn sheep were sighted

in the area after 1948 (Brown 1974). Buechner (1960) reported a similar

trend in the 15 western states historically inhabitated by bighorn sheep.

He found that they occupied approximately 10 percent of their former

range and their numbers were reduced substantially to a 1960 estimate of

less than 20,000. Bighorn sheep were exterminated in four of the 15

states.

In 1959, two transplants of bighorn sheep, totaling 13 ewes and

six rams, were made into the Thompson Falls area. A study of the distri­

bution and population characteristics of the resulting herd was carried

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. out in 1973 and 1974 by Brown (1974). He reported that the herd had

expanded its range to include 140 square miles (363 sq. km) of mountain­

ous terrain and numbered approximately 240 individuals.

Brown’s (1974) investigation identified two herd segments within

the population, with interchange apparently restricted to rams.

Relatively high body weights, rapid horn growth, early physical maturity,

high productivity, and low lungworm levels indicated a healthy population.

Brown’s pilot study to assess the current status of mountain sheep in

the Thompson Falls area resulted in a recommendation for ”a follow-up to

determine the carrying capacity for ungulates, as reflected by range

conditions." Brown postulated that a future population crash was prob­

able due to a rapidly expanding population in a region where severe

winters occur sporadically. He proposed a preventive management program

consisting of an expanded hunter harvest and/or removal of animals for

transplanting stock on a sustained basis to stabilize the population.

The present study of winter habitat relations was designed to provide

information on the critical management question of carrying capacity.

Many other investigators have recognized the importance of winter

habitat characteristics in the ecology of Rocky Mountain bighorn sheep

(Honess and Frost 1942, Smith 1954, Buechner 1960, Oldemeyer 1966, and

Rutherford 1972a). Smith (1954) stated "Just as winter and early spring

is the critical period in the life of the bighorn, so is the abundance

and condition of available winter range a determining factor in his

survival." In his classic monograph on bighorn sheep, Buechner (1960)

stated that the poor conditions of winter ranges in Wyoming and Montana

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. were the principal limitations to population sizes. He recommended

intensive research on crucial winter ranges as essential to bighorn

sheep conservation efforts. Oldemeyer (1966) stated that further

research into bighorn sheep winter ecology was needed. While it should

not be assumed "a priori" that winter range conditions are the limiting

factor for a particular bighorn sheep population, investigations on

this potentially critical seasonal range should probably be given

priority unless local conditions suggest possible limitations on other

seasonal ranges.

Recent studies have yielded some information on habitat use by

wintering bighorn sheep. Oldemeyer (1966) reported small patches of

conifers and deep ravines were often utilized as shelter with the onset

of falling snow and wind. He found that wintering bighorns preferred

south, southwest, and west facing slopes on steep, rocky terrain or

ridge tops. Geist (1971), in discussing the behavior of mountain sheep

on winter ranges, stated "they appear to prefer the warmest elevations

of the mountains, keeping in the warm air above the thermocline." Geist

reported observing bighorn sheep avoiding deep snow except when the

crust supported their weight. Shannon et al. (1975) related seasonal

distribution of ewe-juvenile groups of bighorn sheep to 11 environmental

variables. Stelfox (1975) reported a highly significant positive

correlation between barometric pressure and numbers of sheep on exposed

grasslands during winter. He also found a significant negative correla­

tion between snow depth and numbers of sheep on those ranges. Geist

(1971) stated that as a general adaptation to winter "mountain sheep

s Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. typically reduce waste of energy by avoiding excessive heat loss and

excessive energy expenditures in foraging and social life, while

maximizing energy gain and retention for the lowest possible expendi­

ture. "

Energy relationships between an animal and its environment have

recently received increased attention. Variations in habitat structure

and ambient meteorological conditions that influence energy expenditure

have been reported to influence winter range distribution of several

ungulate species in addition to bighorn sheep. Snow depth and forest

canopy characteristics were reported to be correlated with moose (Alces

alces) and white-tailed deer (Odocoileus virginianus) distribution by

Telfer (1970). Kelsall and Prescott (1971) reported snow depths were

important in determining moose and white-tailed deer distribution.

Gilbert et al. (1970) found snow depths in excess of 18 inches (46 cm)

essentially precluded range use by mule deer (^. hemionus). Interactions

of snow depth and crust hardness were an important parameter in moose-

wolf (Canis lupus) relationships (Peterson and Allen 197 4). Loveless

(1967) observed responses of wintering mule deer to variations in solar

radiation, air temperature, atmospheric moisture, snow conditions,

browse availability, and interspersion of food and cover.

The planning stages of the present study were strongly influenced

by the results of a study by Beall (1974) of elk (Cervus elaphus) winter

habitat selection and use. He reported that feeding site habitat

selection by elk was affected by snow depth, ambient temperature,

radiation, wind velocity, slope position, and timber stand density. lie

\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. also found that elk bedding site distribution correlated with slope,

aspect, slope position, and stand density. Different habitats were

selected under varying meteorological conditions. In addition, elk

had a tendency to bed near the largest tree available in the immediate

vicinity of the bedding site. Potential relationships between charac­

teristics of coniferous tree cover and bighorn sheep bedding sites

have not been adequately investigated. Such information would be useful

in evaluating the impact of logging activities and prescribed burning

programs on bighorn sheep winter ranges.

Quantitative information on ungulate distribution in relation to

ambient meteorological conditions and biotic and abiotic environmental

variables is necessary if the portions of winter range that may be

critical to the survival of animal populations are to be identified.

A better understanding of winter habitat selection would allow concen­

tration of range management efforts on key areas. At the present time,

information concerning the distribution of bighorn sheep on their winter

ranges in relation to potentially important environmental variables is

lacking. Winter habitat selection by many different populations of

bighorn sheep must be investigated in depth if the survival strategies

and capabilities of the species are to be fully understood. Results

from the present study should contribute information toward this objec­

tive.

Information on the use of winter habitat has important management

implications since the transplanting of bighorn sheep into formerly

occupied areas has become a widely used game management technique for

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. increasing distribution and abundance (Yoakum 1963). Rutherford

(197 2a) pointed out that evaluation of potential transplant sites was

complicated by the facts that bighorn sheep were very selective and

their habitat requirements were not well understood. This lack of

knowledge is apparent when the success rate of transplanting, operations

is examined. Although all of the transplant sites in Colorado were

judged to offer excellent opportunities at the time the releases were

made, only eight of 14 transplant sites were occupied in 197 2 by

successful populations (Rutherford 1972b). In Montana, Couey and

Schallenberger (1971) reported that seven transplant sites contained

surviving or huntable populations, five were failures, and the status

of seven other transplants had not been determined. The Thompson Falls

population, the result of a transplanting operation, is a particularly

relevant population for study. Information gained in the present study

may be useful in evaluating potential winter ranges on proposed bighorn

sheep transplant sites.

The present study, designed to investigate winter habitat selection

and use by mountain sheep in the Thompson Falls area, was conducted from

June 1975 through July 1976. Specific objectives were to:

1) quantitatively describe the habitat available to wintering

bighorn sheep;

2) determine winter habitat use by bighorn sheep and other wild

ungulates ;

3) evaluate winter habitat preferences of bighorn sheep in rela­

tion to biotic and abiotic environmental variables;

\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4) characterize bighorn sheep winter bedding site habitat; and

5) quantify forage utilization on key-use areas within the winter

range.

N Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER II

DESCRIPTION OF THE STUDY AREA

Selection

The Thompson Falls bighorn sheep population was well suited for

the present intensive winter study. Brown's (1974) pilot study defined

basic seasonal distribution patterns and population characteristics of

the herd. A number of bighorn sheep, individually marked by Brown,

remained in the population and could provide information on individual

movements and use patterns. The portion of the winter range selected

for the present study offered a wide variety of elevational, topograph­

ical, and vegetatio.nal habitat choices to wintering ungulates. This

diversity within the study area was considered important for evaluating

possible habitat selection by bighorn sheep.

Location and Ownership

The Thompson Falls bighorn sheep range is situated in the southeast

end of the Cabinet Range along the north side of the Clark Fork River

midway between Plains and Thompson Falls, Montana (Fig. 1.). Map

coordinates are 115° 00' - 115° 15' W. longitude and 47° 30' - 47° 45' N.

latitude. For a detailed description of this area see Brown (1974).

The present study was conducted on a 4,102 acre (1,660 ha) portion

of this bighorn sheep range adjacent to State Highway 200 (Fig. 2.).

8

\ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i î Scale in Miles

Flathead V ijte Lake

m f STUDY m fk

M i */-Sfudy Area

MONTANA issoula

Fig. 1. Location of study area,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. H 27 W K 2 6 W

B IG HO LE Planning Unit VICINITY MAP ] Planning Unit Boundary ] National Forest Land ] State & Private Land ^ 23

Ô ® ® Study Area

22

Clark

m à t .

20j

Fig. 2. Location of Big Hole Planning Unit, Lolo National Forest (adapted from Anonymous 1976).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11

The study area is bordered roughly by Weeksville Creek on the east,

Munson Creek on the west. Highway 200 on the south, and on the north,

by the north slope-south slope divide overlooking the Clark Fork River

Valley. The entire study area is within the region bounded by map

coordinates 115° 00'00" - 115° 07'30" W. longitude and 47° 31'25" -

47° 34'36" N. latitude.

The study area is in the Big Hole Planning Unit (BHPU) on the

Lolo National Forest (Fig. 2.), Section 35 and portions of section 36,

T21N, R27W comprise most of the private land. In 1976, the U.S. Forest

Service issued a Draft Environmental Statement concerning the proposed

Multiple Use Plan for the BHPU. That document was a primary source

for information contained in this chapter.

Topography and Geology

Brown (1974) described geologic structure and geomorphic features

for the entire sheep range. The portion of his description relevant

to my study area reveals that local topography was greatly influenced

by massive Glacial Lake Missoula. With the rupture of the glacial ice

dam near Sandpoint, Idaho, the Lake's waters were rapidly discharged

at an estimated rate of 8 to 10 cubic miles (33 - 42 cu. km) per hour

(Alt and Hyndman 1972). Lake sediments and residual soils were washed

from the walls of the narrow Clark Fork Valley between Plains and

Thompson Falls resulting in exposure of parent material. This section

of the Valley is characterized by poorly developed soils and numerous

talus cones emanating from rugged crags of exposed bedrock. From the

Valley floor at approximately 2,400 feet (732 meters), the mountains

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12

rise to over 5,900 feet (1,798 meters) in less than 1.5 miles (2.4 km).

Alden (1953) reported that the gorge transected an anticline composed

mostly of Precambrian quartizite.

The general orientation of the Clark Fork Valley within the study

area is northwest to southeast. As a result, south to southwest

exposures predominate. West and east exposures occur within five

secondary drainages oriented in a north-south direction. Among these

secondary drainages, only Munson Creek and Weeksville Creek have cut

down to the Clark Fork Valley floor. The other three drainages are

hanging valleys whose mouths terminate above 3,400 feet (1,036 meters).

Climate

Climatic characteristics pertinent to the study area have been

described by Brown (1974) and the U.S. Forest Service (Anonymous 1976).

Brown (1974) stated:

"The Clark’s Fork River Valley between Plains and

Thompson Falls reputedly has the mildest weather condi­

tions in northwestern Montana. This is due mainly to the

northwest-southeast alignment of mountain ranges. The

Coeur d'Alene Range to the southwest blocks out much of

the moisture-laden air moving inland from the Pacific

Coast, while the Cabinet Range to the northwest shelters

the area from cold air masses moving south from Canada."

The prevailing flow of air aloft is from the west and southwest

during spring and summer, shifting to more northerly directions during

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13

fall and winter. The study area is therefore dominated by a Pacific

maritime climate characterized by a warm, moist spring and a fairly

long, dry, and hot summer followed by wet, cool fall and winter seasons

(Anonymous 197 6). Precipitation and temperature often vary greatly

within the study area due to marked elevational differences.

Abrupt seasonal and daily changes of weather are common. This

is especially true when continental air masses occasionally overtop

the sheltering Rocky Mountains (Anonymous 1976). This reversal of

normal circulation often results in extremes of temperature and/or

precipitation.

Climatological data for the U.S. Weather Bureau were collected

by the Montana Power Company at their hydroelectric plant in Thompson

Falls, approximately 12 miles (19.3 km) from the study area. During

the 30 year period ending in 1970, the average annual temperature was

47.5° F (8.6° C). January was the coldest month averaging 26.5° F

(-3.1° C) with a range from -36° F (-37.8° C) to 56° F (13.3° C). July o and August were the warmest months with monthly means of 68.5 F

(20.3° C) and 67.2° F (19.6° C), respectively. The range of recorded

temperatures in July was 35° F (1.7° C) to 109° F (42.8 C) in the 30

year recording period.

Mean annual precipitation was 22.5 inches (57.2 cm). November,

December, and January had the most precipitation, with a secondary

peak in June. Snow and ice pellet precipitation records indicated the

highest average amounts in December, January, February, and March.

The average annual precipitation within the study area, as

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estimated by the U.S. Forest Service, varies from approximately

19 inches (48.3 cm) to over 50 inches (127 cm). The precipitation

pattern for the entire BHPU is described in the Draft Environmental

Statement Multiple Use Plan (Anonymous 1976) as follows:

"Total annual precipitation ranges from 19 inches along the Clark Fork River Valley to about 75 inches at the summit of Big Hole Peak . . . This unit is on the edge of a rain shadow area produced by the higher eleva­ tion Bitterroot Mountains to the west. Rain and snow amounts at any given elevation in this planning unit are less than comparable sites to the west, but greater than lands immediately east of the planning unit . . . Distribution of total precipitation between snow and rain is conditioned by season and elevation. Snow accounts for about 25 percent of low elevation precipita­ tion and increases to 70 percent or more along the high ridges and peak areas . . . As elevation increases within the unit it can be assumed that precipitation will increase in amount, intensity and seasonal variance, but the general pattern established at Thompson Falls will likely persist over the entire planning unit."

In order to evaluate the data from the present winter study,

comparison was made of weather conditions during the study period

and those of previous winters. Listed in Table 1 are several

temperature and precipitation parameters recorded at the Thompson

Falls weather station during the 1975-1976 winter, the severe winter

of 1968-1969, and corresponding mean and extreme values for the 30

year period ending in 1970. The 1975-1976 winter was average to mild.

Total winter precipitation was somewhat higher than average, due

mainly to heavy rainfall in December. Temperatures were near normal

for December and February, January was warmer than the 30-year average

and March was cooler. Simultaneous high precipitation and low

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temperatures, characteristic of a severe winter for this weather

recording station, did not occur in any month.

An index of winter severity was calculated for the 1975-1976

winter, the 1968-1969 winter, and the 30-year average using the

method described by Peek et al. (1976). The index was derived by

subtracting the mean monthly temperature from 32° F (0° C), multiply­

ing the remainder by the corresponding monthly precipitation, and

adding the monthly (December through March) products. This method

rated the 1975-1976 winter as slightly less severe (1.36) than the

30-year average (7.94). The 1968-1969 winter had a severity index

of 100.5 at the Thompson Falls weather station. Peek et al. (197 6)

reported a 12-year average in northeastern Minnesota of 89.15. A

winter that rated 7 6.93 during that study was considered about normal.

Severity indexes of 182.15 and 45.76 were judged more severe and much

less severe, respectively, than the 12-year average.

Vegetation

The floristic composition in the Thompson Falls region reflects

the Pacific Coast climatic influence (Brown 1974). Species common to

the west coast such as western red cedar (Thuja plicata), grand fir

(Abies grandis), western hemlock (Tsuga heterophylla), mountain hemlock

(Tsuga mertensiana), and western yew (Taxus brevifolia) occur in the

vicinity of Thompson Falls. Brown reported a species list for his

study area.

The present study area was Included in a vegetation description

of the BHPU based on habitat type inventories (Anonymous 197 6). The

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Table 1. Winter weather data recorded at Thompson Falls, Montana during the study period (1975-1976), a severe winter (1968-1969), and the 30-year period of 1941-1970.

Temperature Mean Extremes Total Period Monthly Precipitation Temperature (inches) (°F) Max imum Min imum

1975-1976 December 30.4 49 6 4.00 January 30.3 48 4 2.54 February 33.1 55 3 2.54 March 35.8 68 5 1.73

1968-1969 December 25.2 43 -25 3.58 January 19.4 40 —6 6.14 February 29.0 46 9 1.04 March 36.6 67 7 1.07

1941-1970 December 30.1 68 -25 2.50 January 26.5 56 -36 2.61 February 33. 0 64 -30 1.85 March 38.0 78 -10 1.72

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classification of habitat types on the basis of potential climax

tree species and characteristic understory plants was according to

Preliminary Forest Habitat Types of Western Montana (Pfister et al.

1972). The habitat types were then grouped according to Habitat

Type Inventory Standards and Procedures for Multiple Use Planning

(Anonymous 1973). The study area was classified primarily as rockland

and scree by this broad habitat group system. Small areas of the

Douglas—fir (Pseudotsuga menziesii)/shrub group were identified at

middle to high elevations. The queencup beadlilly (Clintonia

unlflora) group, containing grand fir and western red cedar, was

restricted to stream bottoms. The ponderosa pine (Pinus ponderosa)

and dry beargrass (Xerophyllym tenax) groups were reported on the

periphery of the study area at low and high elevations, respectively.

Detailed descriptions of each habitat group may be found in Brown (1974)

and Anonymous (1976).

Fire History

An analysis of the BHPU (Anonymous 1976) by the U.S. Forest

Service stated: "Fire has greatly influenced life forms in the plan­

ning unit. Almost all the present plant and animal species in the

natural ecosystem are dependent on fire for their perpetuation. Some

plant species require fire's heat to open seeds or provide openings

for regeneration and growth."

Evidence of past fires are found throughout the study area

(Fig. 3). Much of the Munson Creek Drainage burned in 1889. In 1945,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FIRE OCCURRENCE

Major f\f9 Boundary Spot fire Location: » 1940 - 45 -S' 1946 - 50 p 1951 - 55 1914 'é ' 1956 - 60 I 1961 - 65 1966 - 70 7 1971 - 74

\

1889' / 1889 18 84 \ /] /' yi9i7 ‘ 1924

t" 19 45

j ' National foreal Land

Slate and Private Land __ ^ 11917 / BIG HOLE PLANNING UNIT

Fig. 3. Fire history of the Big Hole Planning Unit, Lolo National Forest (adapted from Anonymous 1976) .

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over 600 acres (242.8 ha) burned along the Clark Fork Face, including

nearly all of one upper elevational valley. Numerous spot fires

occurred throughout the study area.

Land Use

Timber resources on the federally owned land within the BHPU

were inventoried by the U.S. Forest Service (Anonymous 1976). The

steep, rocky face along the Clark Fork River Valley, which comprised

the major part of the study area, was classified non-forest and non­

commercial forest. Potential timber producing areas of seedlings,

poles, and sawlogs, primarily at higher elevations, were identified.

Section 35 and the portion of Section 36, T21N, R27W, within the study

area contain both sawlog and non-commerical forest land. This

privately owned land is the only part of the study area that has been

logged.

Currently one National Forest grazing allotment is issued in

the Munson Creek area. Section 35 and a portion of Section 36 T21N,

R27W have been grazed by cattle for several years.

The BHPU is not considered a significant area for recreation in

the Lolo National Forest (Anonymous 1976). The pressure on the study

area for day hiking and overnight camping is limited because of steep

topography, limited trail and road development, and scarcity of water.

The hunting of bighorn sheep, mule deer, white-tailed deer, and black

bear (Ursus americanus) results in light recreational use. Viewing

of bighorn sheep along Montana Highway 200, particularly in the spring

and early summer, is the major recreational use of the study area.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER III

MATERIALS AND METHODS

Capture and Marking Techniques

Brown (1974) reported 19 bighorn sheep marked with rope-flagging

collars in the Thompson Falls population as of April 1974. 1

trapped during the summer of 1975 in an attempt to complete marked

cohorts for all sex and age classes. A portable corral type trap

(Bodie and Hickey 1976), provided by the Idaho Department of Fish

and Game, was installed at a heavily used lick site previously

located by Brown (1974). A clover trap provided by the Montana Fish

and Game Department was installed in close proximity to the corral

trap for use as a holding pen for lambs. The corral trap was baited

with two 50 pound (22.7 kg) blocks of salt (NaCl 99 percent, inert

matter 1 percent). A manually operated triggering device allowed

selectivity in number and age-sex composition of animals captured.

Trapped animals were manhandled and their legs secured in a fash­

ion similar to that of tying up a calf. Tranquilizing drugs were not

used. Each animal was marked with a color-coded rope-flagging collar

(Craighead et al. 1969). Each collar consisted of four flags in

combination with white rope for males and yellow rope for females.

Each collar included either a reddish brown or black numbered pendant.

20

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which facilitated individual identification at close range. The four

color-coded flags identified animals at longer distances. Inside

circumferences of collars were 24 inches (61 cm) for ewes and 28

inches (71 cm) for rams, as recommended by Brown (1974).

Live weights were obtained, when possible, with a Chatillion

type-160 spring scale. Observations of marked sheep provided data on

home ranges, daily movements, and habitat use.

Temperature and Snow Measurements

Four recording thermographs provided continuous temperature

records at 2,700; 3,500; 4,300; and 5,100 feet (823; 1,067; 1,311,

and 1,555 m) elevations on open south to southwest slopes. The thermo­

graph data provided an accurate means of determining temperature at

times of sheep observations. The thermographic records were also

useful for identification of inversion conditions characterized by

warming temperatures with increasing elevation.

Snow measurement stakes were erected to sample snow depths at

approximately 400 feet (122 m) elevational intervals on south to

southwest aspects of the study area. Snow stakes were placed in both

open forest and closed forest plant cover types at each elevation.

Similar stations were placed at 3,100; 4,300; and 5,100 feet (945;

1,311; and 1,555 m) elevations on east and west aspects.

Observations of Ungulate Distribution

From 1 January to 30 March 1976, animal use was assessed by direct

ground observations of ungulates and ungulate signs (tracks, beds, and

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fecal groups) from five predetermined routes. Four routes, selected

to collectively sample the entire study area, were covered on foot.

One vehicular route consisted of nine predetermined observational

points adjacent to Highway 200.

The routes were traveled at intervals of approximately 1 week.

Each route traveled on foot took an entire day to complete. The

vehicular route was traveled in the afternoon as this was the time of

greatest sheep activity (Brown 1974). Fifteen to 30 minutes were

spent at each highway observational point. The vehicular route was

traversed in opposite directions during alternate counts.

The open nature of the Clark's Fork face facilitated direct

ground observations. However, bighorn use of dense timber stands was

potentially underestimated by this method. Fortunately, the majority

of closed forest stands on the study area occurred at higher elevations

where snow conditions usually permitted the collection of track data

in addition to direct observational data.

Direct observations were aided by the use of 7 x 26 mm binoculars

and a 15-60x variable spotting scope. Upon initial observation, the

time of day, location, type of activity, abiotic and biotic habitat

characteristics, meteorological conditions, age and sex composition,

and number of marked animals were recorded numerically for each group.

Identity of marked animals, notes on behavior, and reobservations

were entered on the back of 3 x 5 inch (7.6 x 12.7 cm) datum cards.

Only one record per day was made for each group.

No attempt was made to distinguish between male and female lambs

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or yearling and adult females. Hales 18 months and older were divided

into horn length classes (Geist 1971). These males were recorded as

yearlings ( < 1/2 curl), young rams 1/2 < 3/4 curl), or adult rams

( ^ 3/4 curl).

The activity of the group when first spotted was categorized as

bedding, feeding, bedding and feeding, standing alert, traveling, or

fleeing. Traveling was defined as animals actively engaged in moving

from one location to another at a walking pace. Fleeing consisted of

animals running from one location to another.

Each group sighting was located on a USGS 7.5 minute topographic

map overlaid with a 0.1 mile (0.16 km) grid. A four digit numerical

coding scheme with the first two digits identifying individual square

mile portions of the study area and the last two digits identifying

0.1 mile (0.16 km) east-west and north-south coordinates within each

square mile was employed to record each location. The location was

recorded numerically as the nearest grid intersection point.

Movements and Home Range

Movements, winter centers of activity, and minimum home range

sizes for marked sheep were determined from ground observational data.

The centers of activity for Individually tagged animals were defined

on topographic maps using a grid overlay system as explained by Hayne

(1949). The centers of activity were used with Harrison's (1958)

formula (SD = Jg D^/N) to calculate the standard diameter (SD) for

each marked animal. D is twice the distance from the center of activ­

ity to each relocation, and N is the total number of relocations.

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The standard diameter represents the diameter of a circle with

the center of activity as its center, and which contains 68.26 percent

of all relocations of an animal during the period considered. Re­

locations plotted on gridded topographic maps were connected to

delineate individual minimum winter ranges. Areas of resulting

polygons were measured with a polar planimeter (Craighead et al. 1973)

to determine minimum winter home range sizes.

Vegetation Analysis

Existing vegetation description. A plant cover type classifi­

cation scheme based on physiognomy and vegetational characteristics

of potential importance to wintering bighorn sheep was developed for

the study area. A minimum of 25 percent coniferous canopy cover

was considered necessary for a community to be classified forest

(Penfound 1967). Any land on which shrubs dominated the vegetation

was considered shrubland. Lands dominated by grasses or grass-like

plants were classified as grasslands. Canopy cover was the sole

measure of dominance used to distinguish between cover types. The

five plant cover types recognized within the study area are described

below.

1) Rockland is characterized by a non-bryoid canopy coverage

total of less than 25 percent. This type is essentially identical

to Penfound's (1967) bryoland. The vegetative canopy cover is dominated

by lichens growing on relatively stable talus slopes or rock outcrops.

2) Shrubland-Grassland Complex is characterized by canopy

coverages of 0-24 percent for conifers, 25-100 percent for shrubs, and

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1-75 percent for perennial bunch-habit graminoids. There are no

large expanses of grassland on the study area. Graminoid cover

varies dramatically with soil conditions and bluebunch wheatgrass

(Agropyron spicaturn), rough fescue (Festuca scabrella), and elk

sedge (Carex geyeri) are locally abundant in this cover type. The

Shrubland-Grassland Complex plant cover type is found at all

elevations and on all aspects of the study area.

3) Open Forest is characterized by canopy coverages of

25-75 percent for conifers, 5-75 percent for shrubs, and 5-75 percent

for perennial bunch-habit graminoids. Open forest occurs at all

elevations on south to west facing slopes.

4) Closed Forest is characterized by canopy coverages of

76-100 percent for conifers, 1-100 percent for shrubs, and 0-4 percent

for bunch-habit graminoids. Closed forest communities occur as

stringers and islands at low elevations. At elevations above 3,500

feet (1,067 m), this type is found in extensive communities on east,

west, and north slopes.

5) Riparian communities are characterized by the presence of

broadleaf tree species such as black cottonwood (Populus tricocarpa),

alder (Alnus spp.), willow (Salix, spp.) and quaking aspen (Populus

tremuloides). The largest riparian community (6 acres; 2.4 ha) occurs

on a wide bench at 3,200 feet (97 5 m) elevation in the Weeksville

Creek area. Small stands of quaking aspen, a minor type on the study

area, occur sporadically at the base of talus slopes.

Conifer canopy cover, conifer stand structure characteristics.

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shrub cover, and graminoid cover were sampled systematically on a

portion of the study area containing representative examples of the

four important plant cover types. Since the entire study area was

not randomly sampled, the data generated should be viewed as only a

general description of each cover type.

Conifer stem density was measured by the. point-centered quarter

method (Cottara and Curtis 1956) with the distances measured by a

rangefinder for distances less than 100 feet (30.5 m) and estimated

to the nearest 25 feet (7.6 m) for distances greater than 100 feet

(30.5 m). To provide estimates of basal area, the dBH class of each

tree encountered in the density measurements was recorded as 0-5 inches

(0-12.7 cm), 5-11 inches (12.7-27.9 cm), 11-21 inches (27.9-53.3 cm),

or > 21 inches (>53 cm). Crown canopy cover was measured with a

Model C forest densiometer (Lemmon 1957).

Circular plots of 0.01 acres (0.004 ha) were used to provide

canopy coverage class estimates for individual shrub species and the

perennial bunch-habit graminoid group. The coverage classes in percent

cover were Trace (< 1%), 1-5, 5-25, 25-50, 50-75, 75-95, and 95-100.

Potential vegetation description. In recent years, land manage­

ment agencies in the Northern Rocky Mountain region have used habitat

type methods of land classification extensively for resource management

purposes. Daubenmire and Daubenmire (1968) developed a habitat type

classification system for forests of northern Idaho and eastern

Washington. Pfister et al. (1974) developed a similar system for

forested lands of Montana.

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A habitat type is "the aggregation of units of land capable

of producing similar plant communities at climax . . (Pfister et al.

1974). Each forest habitat type is designated by a two component

label representing the dominant tree species and the dominant or

characteristic undergrowth species in the climax community (i.e.,

Pseudotsuga menziesii/Physocarpus malvaceus habitat type). Daubenmire

and Daubenmire (1968) explained the reasoning behind an overstory/

understory classification scheme as follows:

"In the northern Rockies, forest overstory and under­ growth occupy the land independently . . . The composition of the tree stratum at climax is more closely relatable to macroclimate than to soil. The undergrowth unions are relatively more sensitive to soil and microclimate than are the trees."

The utility of habitat types in forest management is explained

by Pfister et al- (1974) as follows:

"They provide a permanent and ecologically-based system of land stratification. Each habitat type encompasses a certain amount of environmental variation but the variation within a particular habitat type should generally be less than between types. Plant succession can be predicted for each habitat type and a similar response to management treat­ ments can be expected on units of land within the same type."

This predictability of plant succession and response to management

by habitat type holds great promise of applicability to wildlife

management. Information on seasonal animal distribution and use of

plant cover types and habitat types is necessary for the evaluation

of relationships between plant succession and animal species. When

these relationships are understood, the habitat type classification

system may prove a valuable tool for resource managers concerned with

the long-term management of wildlife populations.

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The study area was categorized according to the habitat type

classifications of Pfister et al. (1974). A habitat type map was

drafted interpretively utilizing ground truth data, aerial photos,

and topographic maps. The maximum allowable inclusion of other

types within a mapping unit was 20 percent.

Determination of Habitat Use

Fifteen abiotic and four biotic environmental variables were

considered as potential determinants of bighorn sheep spatial dis­

tribution on the winter range. These variables were measured in

conjunction with all group sightings.

The abiotic factors considered and the methods of measurement

are described below.

1) Elevation was measured to the nearest 10 feet (3 m) with a

Thommens pocket altimeter.

2) Slope steepness was estimated from topographic maps and

recorded as percent slope classes of 0-10, 10-35, 35-60, 60-80, and

> 80.

3) Topographic position was characterized as drainage bottom,

lower slope, middle slope, upper slope, ridge, or cliff.

4) Aspect was measured with a Silva compass and recorded as

N, NE, E, SE, S, SW, W, or NW.

5) Distance to the nearest cliff was measured in feet with a

rangefinder if less than 100 feet (30.5 m) and was estimated to the

nearest 25 feet (7.6 m) if greater than 100 feet (30.5 m). A "cliff"

was defined as a vertical drop of at least 15 feet (4.6 m).

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6) Distance to steep terrain areas of more than 80 percent

slope and larger than 4 acres (1.6 ha) was measured on topographic

maps and recorded to the nearest 0.1 mile (0.16 km).

7) Temperature at the time of each group sighting was estimated

from the recording thermograph data and recorded in °Kelvin (°C + 273).

For sightings at elevations bracketed by thermograph stations (2,700

to 5,100 feet, 823 to 1,554 m), temperature was estimated by linear

interpolation. If an inversion existed between two stations, it was

assumed to occur exactly at the elevational midpoint between them.

For sightings below 2,700 feet and above 5,100 feet (823 to 1,554 m)

elevations, temperature was estimated by linear extrapolation assuming

a lapse rate of 2 degrees Centigrade per 1,000 feet (305 m) elevational

change.

8) Snow character was classified as powder, bottom crust, top

crust, or wet. Depth of sheep tracks were measured when possible to

provide an indication of crust support characteristics.

9) Wind condition was recorded as calm, steady, or gusty.

10) Wind direction was estimated with a Silva compass and recorded

as N, NNE, NE, ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, NW, or

NNW.

11) Wind speed was measured with a Dwyer wind meter and maximum

and minimum values in a 2 minute period recorded in miles per hour.

12) Cloud cover was estimated by percent coverage classes of

0-10, 11-50, 51-90, and 91-100.

13) Precipitation was recorded as none, rain, sleet, hail, or snow.

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Barometric pressure was obtained from a barograph housed

approximately 12 miles (19,3 km) from the study area.

15) Barometric pressure trend for the 4 hours preceding each

sighting was recorded as the slope of the line on the barograph

record for that time period. Increasing pressure was recorded as

positive and decreasing pressure as negative.

The biotic environmental variables recorded in conjunction with

group observations are described below.

1) Cover type in the vicinity of each group of animals was

recorded as rockland, shrubland, shrubland-grassland complex, open

forest, closed forest, or riparian.

2) Habitat type in the vicinity of each group sighting was

determined through the use of cover type data and a habitat type

map of the study area.

3) Distance to the nearest conifer was measured with a range-

finder for distances less than 100 feet (30.5 m) and estimated within

25 feet (7.6 m) for greater distances.

4) Conifer canopy coverage class in the vicinity of each group

was estimated and recorded in percent as 0-24, 25-75, or 76-100.

Bedding Site Habitat Analysis

Bedding sites were encountered in conjunction with ground

censusing activities and during search periods devoted primarily to

their location. Back-tracking of animals in fresh snow and direct

observation of animals served to identify individual beds. Use of

each bed was estimated as occurring in the previous 4, 24, or 48 hours.

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or classified as unknown. When possible, sites were also classified

as day beds or night beds. Nine abiotic and seven biotic environ­

mental variables were measured at each bedding site.

The abiotic environmental variables considered and the methods

of measurement are described below.

1) Elevation, slope, topographic position, aspect, distance to

the nearest cliff, and snow character were recorded in the same manner

as for group observations.

2) Width of ledge or ridge was measured with a rangefinder in

appropriate topographic positions.

3) Snow depth was measured in centimeters at five locations in

the vicinity of the bed and the results averaged.

The biotic environmental variables considered and the methods of

measurement are described below.

1) Cover type and habitat type were recorded in the same manner

as for group observations.

2) Conifer stem density and basal area were determined by the

point centered quarter method with the bed as the sample point; dBH

classes utilized were identical to those used for stand structure

measurements.

3) Conifer canopy cover was measured with a Model C forest

densiometer (Lemmon 1957) while standing in the center of the bed.

4) Distance to the nearest conifer and dBH class of the nearest

conifer were determined from the point-centered quarter data.

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Pellet Group Distribution

Ungulate fecal groups on a representative portion of the study

area were sampled with 20 foot (6.1 m) diameter circular plots. A

restricted random design was used to locate six transects along

slope contours between 2,650 and 5,150 feet (808-1,570 m) elevation.

One transect was located along a north-south ridgetop and sampled

from 2,700 to 5,150 feet (823-1,570 m) elevation. The position of

the initial plot on the ridgetop transect was located randomly. All

of the transects were located on predominately south to southwest

aspects in areas where sheep use during the winter was expected.

Pellet group plot centers were located 100 feet (30.5 m) apart

and were marked with metal stakes. Plots were cleared of all fecal

groups in December and the numbers of fecal groups deposited during

the winter were counted in the first week of April. An ungulate fecal

group was considered to be five or more pellets of the same general

size, shape, hardness, and color (Bowden et al. 1969). Groups

occurring on the plot periphery were counted if one half or more of

their total area fell within the plot.

At the time of the spring count, numerous site factors associ­

ated with each plot were recorded. The abiotic factors measured were

elevation, topographic position, and distance to the nearest cliff.

The biotic factors measured were cover type, conifer stem density,

conifer canopy cover, and canopy coverage classes for total shrubs,

individual shrub species, and total perennial graminoids. Methods of

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measurement and coverage classes were identical to those previously

described for the group sighting and bedding site analysis.

Fecal pH

Within the study area, bighorn sheep and mule deer occupied

overlapping winter ranges. Therefore, pellet group counts used to

investigate bighorn winter range use are subject to error unless

fecal groups can be reliably separated by species. Since external

examination of ungulate pellets is not always a reliable method of

species identification (Neff 1968), fecal pH was investigated as a

possible method of differentiation in the present study (Howard 1967,

Nagy and Gilbert 1968, and Krausman et al. 1974).

Fecal groups were collected from the exclusive winter ranges of

mule deer and bighorn sheep. Permanent plots established and cleared

in December were revisited in early April, and 50 pellet group samples

collected from each range. Samples were air-dried for approximately

2 months at room temperature. Two grams of each sample were crushed

with a mortar and pestle and placed in 30 ml of demineralized water

and stirred vigorously. After a 10 minute soaking period, the samples

were filtered through standard number 41 filter paper and the pH of

the solution determined with a Corning Model 7 pH meter.

Food Habits

Fifty bighorn fecal groups were collected throughout the winter

after direct observation of defecating animals. Pellet groups were

air dried at room temperature for approximately 8 months. Two pellets

were selected randomly from each pellet group collected to form a

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composite winter bighorn fecal sample. This composite sample was

then crushed and mixed well. Twenty randomly selected portions of

the composite sample were sent to the Composition Analysis Laboratory,

Ft. Collins, Colorado, for identification and quantification of

plant fragments in the feces (Sparks and Malechek 1968). Four

hundred microscopic fields on a binocular microscope at lOOx were

examined and average percent relative densities calculated for plant

species present. Research by Todd and Hansen (1973) and Dearden et

al. (1975) suggests that percent relative density figures may nearly

approximate the percentage dry weights in the diet.

Forage Utilization

Browse utilization for serviceberry (Amelanchier alnifolia),

mountain maple (Acer glabrum), bitterbrush (Purshia tridentata),

and chokecherry (Prunus virginiana) was estimated by a twig-count

technique (Shafer 1963) with utilization expressed as percentage of

twig numbers browsed. The term "twig" was defined as that portion

of a branch developed during the last growing season (Stickney 1966).

Five winter range areas were sampled with three transects each. The

location of each transect was determined in a restricted random manner

The selection of sample twigs for counting purposes was similar to

the method of Stickney (1966). In each 20 foot (6.1 m) section of a

transect, the individual shrub of each desired species closest to

the transect line but not farther than 20 feet (6.1 m), was selected

as the sample plant. The major branch or stem with at least 10 twigs

of current growth between 1 and 4 feet (30.5-122 cm) above the ground

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that was nearest the transect line was selected as the sample "twig

cluster". Browsed and unbrowsed twigs within that twig cluster

were then counted. If no single stem of the selected plant had the

minimum 10 twigs, then the branch nearest the transect line was com­

bined with the nearest adjacent stem or stems to constitute the

sample twig cluster.

In addition, 50 sample twig clusters each of serviceberry and

mountain maple were randomly selected for measurement of browsed

and unbrowsed twig lengths in inches. This yielded estimates of

average lengths for browsed and unbrowsed twigs. These estimates

were then combined with the percentage of twig numbers browsed to

estimate the percentage of available total length removed by browsing.

The degree of utilization by herbivores was also estimated for

bluebunch wheatgrass, the dominant perennial graminoid on the study

area. Bluebunch wheatgrass was estimated to constitute approximately

90 percent of the perennial graminoid cover on the study area. Rough

fescue was locally abundant in the Munson Creek area. Pine grass

(Calomagrostis rubescens) was found in some forest stands and elk

sedge was present at higher elevations. Idaho fescue (Festuca

idahoensis) was present but scarce on the study area.

Four winter range areas were sampled for bluebunch wheatgrass

utilization with the same transects utilized in the browse utilization

analysis. One bluebunch wheatgrass plant was sampled every 10 feet

of transect. The plant closest to a mark on the investigator's right

boot was classified as grazed or ungrazed, the height of grazed and

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ungrazed portions of the plant measured, and an estimate made of

the percentage of the total canopy cover grazed. In addition, 15

ungrazed plants were collected and weighed in 10 percent intervals

to establish a height removed/weight removed relationship for bluebunch

wheatgrass on the study area. Using the method of "least squares"

described by Mendenhall (1971), a linear regression line was

developed for the raw data and for an appropriate transformation of

the data. An estimate of utilization by weight was then computed.

Availability Sample of the Study Area

Since the study area is composed of mountainous terrain with

diverse vegetation and many complicated patterns of habitat availa­

bility, a random point method of sampling was employed (Marcum 1975).

The borders of the study area were selected to include only those

lands that were visible from the census routes and thus were examined

at least weekly for use by bighorn sheep. Utilizing the four digit

location code developed for recording bighorn sheep group observations,

150 points were selected for initial sampling through the use of a

random numbers table. The estimated proportion of the study area in

each habitat category was then determined by locating these points on

topographic maps and aerial photographs. These proportions were

treated as binomial parameters and the number of points needed to

estimate each habitat category to within -0.05 of the true proportion

at the 95 percent confidence level was determined (Mendenhall 1971).

Since 244 random points was the largest number required in any habitat

category for the level of accuracy desired, 94 additional locations

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within the study area were selected from a random numbers table.

The proportion of total random points (244) in each habitat category

was then determined.

The distribution of points over the study area was tested for

randomness by dividing the area into five subunits. The area of

each subunit was then determined with a compensating polar planimeter.

The proportion of the total study area occupied by each subunit was

multiplied by the total number of random points in the availability

sample to determine the expected number of points in each subunit if

the distribution was random. A chi square test led to the conclusion

that the availability sample was randomly distributed over the five ? o subunits of the study area (X = 1.69, tabular X = 9.49, p = .05,

4 d.f.).

The accuracy of the study area availability sample was tested

by comparing the random point predictions with polar planimeter

measurements of three mappable habitat categories. The categories

tested were elevations below 2,410 feet (735 m), elevations from 2,410

(735 m) to 2,800 feet (853 m ) , and areas having a slope steepness

greater than 80 percent.

Data Analysis

Data obtained in conjunction with group observations, pellet plots,

and bedding sites were numerically coded in the field and subsequently

punched on computer cards. A DEC-10 digital computer system and the

SPSS (Statistical Package for the Social Sciences) system of computer

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programs (Nie et al. 1975) were used for summary and analysis of

the data.

The chi-square technique was used to test the hypothesis that

bighorn sheep utilized habitat categories (i.e., rockland, shrubland)

in exact proportion to their occurrence on the study area. If this

hypothesis was rejected (p = 0.005), individual habitat categories

were examined by the method of Neu et al. (1974). The term

"preference” was utilized to describe a situation in which bighorn

sheep use of a habitat category was significantly greater than its

availability within the study area. The term "avoidance" was used

to describe a situation where bighorn use was significantly less

than availability. "None" was employed to denote the apparent

selection behavior when use was not significantly different from

availability. A significance level of 0.10 was used In constructing

simultaneous confidence intervals on proportions of use in each

habitat category.

To evaluate relationships between meteorological conditions and

habitat use, Pearson product-moment correlation coefficients were

determined for independent meteorological variables versus elevation,

distance to the nearest 15-foot (4.6 m)-minimum cliff, distance to

the nearest conifer, number of bighorns bedding, number of bighorns

feeding, and group size. Analysis of variance (Mendenhall 1971) was

utilized to compare mean values of dependent variables during varying

meteorological conditions.

The thermograph records provided a method of determining when

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temperature inversions occurred on the winter range. A t-test was

used to compare mean elevations of group observations during

inversion and non-inversion conditions. Observations included in

the inversion group were those that occurred when increasing temper­

atures were recorded from 2,700 feet (823 m) up to at least 4,300

feet (1,311 m) elevations.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV

RESULTS

Existing Vegetation

Table 2 provides comparative data on vegetation for the four

major cover types found on the study area. Important shrub species

were those which attained a mean coverage value of 1 percent or

more on at least one major plant cover type. Mean canopy coverage

class values were computed by assigning each cover class a value

equal to the midpoint of that class. Mean coverages were then com­

puted for each plant species and reported as the coverage class in

which they fell.

Potential Vegetation

Nine different forest habitat types and one special topo-

edaphic situation (Pfister et al. 1974) were found within the study

area. Some habitat types occurred as intricate mosaics of potential

climax communities. These areas were mapped as "complexes” of the

repeating habitat types occurring within them. Twelve unique

categories were utilized for mapping purposes (Fig. 4) and are

described below.

1) Rockland-scree comprises approximately 30 percent of the

study area (Fig. 4). Pfister et al, (1974) described scree as

40

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T.ible 2. ComparlHon of tlie four major plant cover types on the winter range.

Plant Cover Type

Shrubland- Rockland Grassland Open Forest Closed Forest

Conifers^ Minimum stems/acre 1 1 1 120 Maximum steras/acre 74 48 155 880 Mean stems/acre ^ 7 7 26 286 Me .an basal area (ff/acre) 9.6 7.5 34.0 165.0 Mean distance nearest conifer (ft/m) 74/22.6 62/18.9 17/5.2 4/1.2

Grasses Agropyron spicatuin Trace^ 5-25% 5-25% 1-5% Calamaerostls rubescens -- Trace 5-25% Festuca scabrella*^ - 1-5% 1-5% -

Shrubs Acer Êlabrum Trace 1-5% 1-5% - Anielanchier alnlfolia Trace 5-25% 1-5% Trace Ceonothus velutinous Trace 1-5% Trace - Chrysothamnus nauseasus Trace 1-5% Trace - Holodiscus discolor - Trace - 1-5% Mahonia repens --- 1-5% Philadelphus lewisii Trace 1-5% 1-5% Trace Physocarpus valvaceus Trace 5-25% 1-5% 25-50% Prunus vlrglniana Trace 1-5% 1-5% - PursViia tridentata Trace 1-5% 1-5% - Ribes spp- Trace Trace Trace - Spirea betullfolia --- 1-5% Svmphoricarpos aibus -- Trace 25-50% Total shrubs 1-5% 2-25% 5-25% 50-70%

Number plots sampled 29 120 53 23

^Plnus ponderosa and Pseudotsuga menzlesll

Less than 1 percent

^Festuca scabrella is found primarily In the Munson Creek area

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%

C/î o3

CD 8 â'

i3 CD

C7X

■OCD O Q. C a O 3 "O O

CD D.

O C «^..StUDr A«CA «OUNOAftr HAAITAT TT^CS ■o I «OCKlAMO-SCACt T Df/CAIU CD sc;*a iN MiUS t OF/AHMA « Or/CV^H en(g ) OF/STAl 4 AF/»fKf(S o" A PP/PUIR 10 OF/AQSP-«OCKUNO-SCtn 3 9 P(/A6SP II O^/AOSP-DF/PHMA-tOCKiAMO-S^tEf

n Df/’PHMA'DfyflSC'-KOCKlAMO-KlfE

Fig. 4. Map of forest habitat types and habitat type complexes occuring on the study area. 43

• - . steep slopes (greater than 30 degrees) composed primarily of

fine rock. Soil profile development is very weak due to the continual

downslope movement of rock fragments." The study area also contains

large areas of rock outcrops and stable rubble slopes that exhibit

little soil development. These "rocklands" do not appear capable of

supporting enough conifers to constitute the 25 percent canopy cover

considered necessary by Pfister et al. (1974) for classifying a

plant community as a forest. Rockland scree is not appropriately

described as a forest habitat type since it represents special topo-

edaphic situations that preclude development of normal successional

trends (Pfister et al. 1974).

Rockland-scree occurs predominately on south to southwest slopes

below 5,000 feet (1,524 m) and is vegetated primarily by the shrubland-

grassland and rockland plant cover types. Douglas-fir (Pseudotsuga

menziesii) and ponderosa pine (Pinus ponderosa) are the dominant tree

species. Serviceberry, mountain maple, ninebark (Physocarpus malvaceus)

mockorange (Philadelphus lewisii), bitterbrush, chokecherry, and

evergreen ceonothus (Ceonothus velutinus) are the most abundant shrubs.

Graminoids are very poorly represented.

2) The Douglas-fir/ninebark (DF/Phma) habitat type is found on

relatively cool and moist slopes, particularly at higher elevations

(Fig. 4). Except for areas recently burned, this habitat type is

generally occupied by a closed timber cover type of Douglas-fir with

occasional western larch (Larix occidentalis) and ponderosa pine.

Ninebark dominates the undergrowth at lower elevations while pine grass

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and elk sedge dominate at higher elevations. Oceanspray (Holodiscus

discolor), snowberry (SymphorIcarpos aIbus), white spirea (Spirea

betulifolla), and heartleaf arnica (Arnica cordlfolia) are common.

3) The Douglas fIr/snowberry (DF/Syal) habitat type, snowberry

phase. Is found predominately at elevations below 4,000 feet (1,219 m)

on gentle to steep southerly slopes with some soil development (Fig.

4). This type often extends as forested stringers up steep rubble

slopes. The DF/Syal/Syal habitat type occupies approximately 13 percent

of the study area. The classification of this type was difficult on

steep slopes because It was necessary to make assumptions about the

climax conifer canopy cover In order to select a site representative

of climax for sampling. Due to the presence of a dense overstory

canopy on a stringer of DF/Syal/Syal habitat type on the study area,

I assumed that a closed canopy would develop on similar sites. , If

a closed canopy had not been assumed, the presence of ninebark and

oceonspray In canopy openings would have resulted In classification

of many areas as DF/Phma, rather than DF/Syal/Syal.

Portions of this habitat type that are occupied by the

closed forest cover type are dominated by medium diameter Douglas-fir.

The understory is dominated by snowberry, white spirea, and Oregon

grape (Mahonia repens). Small amounts of serviceberry, chokecherry,

bluebunch wheatgrass, and plnegrass may also be present. The portions

of the DF/Syal/Syal habitat type now occupied by rockland, shrubland-

grassland, and open forest cover types are very different florlstlcally

and structurally from the more successlonally-advanced closed-tlmber

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areas. The more open cover types commonly contain substantial

amounts of bitterbrush, serviceberry, mountain maple, ninebark, and

chokecherry in tlie shrub layer. Cluebunch wheatgrass is locally

abundant. Openings containing bare rock, shrubs, and bluebunch wheat­

grass are interspersed with small patches of closed forest.

4) The ponderosa pine/bitterbrush habitat type, Idaho fescue

phase, is found on approximately 0.4 percent of the study area near

the mouth of Munson Creek (Fig. 4). This habitat type occurs on a

ridge and slope l>elow 3,700 feet (1,128 m) with a southwest aspect

and is now occupied by open forest and shrubland-grassland plant

cover types. Ponderosa pine is the dominant conifer with Douglas-

fir occurring sporadically on moist microsites. Bitterbrush is

the dominant shrub and serviceberry, chokecherry, mockorange, and

redstem ceonothus (Ceonothus sanguineus) are well represented.

Idaho fescue, rough fescue, and bluebunch wheatgrass are the most

abundant graminoids. Arrowhead balsamroot (Balsamorhiza saggitata)

is the most conspicuous forb.

5) The Douglas-fir/bluebunch wheatgrass (DF/Agsp) habitat type

represents the warm, dry extreme of the Douglas-fir climax series

(Pfister et al. 1974). This habitat type occurs on the study area

on southerly exposures up to approximately 5,100 feet (1,554 m)

elevation (Fig. 4). The overstory is dominated by scattered, large

dBII Douglas-fir and ponderosa pine. G rami no id canopy coverage is

dominated by bluebunch wheatgrass. Bitterbrush, mockorange, service­

berry, mountain maple, chokecherry, currant (Ribcs spp.), oceanspray.

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arrowleaf balsamroot, and yarrow (Achillea millefolium) are often

present. The DF/Agsp habitat type on the study area is presently

occupied by the shrubland-grassland and open forest plant cover types.

6) The Douglas-fir/white spirea (DF/Spbe) habitat type covers

approximately 0.4 percent of the study area. This habitat type occurs

on a relatively gentle middle-slope area near Weeksville Creek

(Fig. 4) and is currently occupied primarily by the closed timber

cover type. A small portion of the area has been disturbed by logging.

Douglas-fir dominates the overstory with occasional ponderosa pine

present. White spirea dominates the understory. Pinegrass and elk

sedge are often present.

7) The Douglas-fir/pinegrass (DF/Caru) habitat type, kinnikinnick

(Arctostaphylos uva-ursi) phase, comprises approximately 1.2 percent

of the study area. A closed forest cover type dominated by ponderosa

pine with ponderosa pine and Douglas-fir seedlings present occupies

this type. Pinegrass is the most abundant understory species, with

white spirea, chokecherry, snowberry, and kinnikinnick present.

8) The grand fir/queencup beadlilly (GF/Clun) habitat type,

queencup beadlilly phase, occupies a small portion of the study area

(0.8 percent) immediately adjacent to Munson Creek (Fig. 4). This

habitat type is occupied by a closed forest cover type dominated by

Douglas-fir with grand fir and western larch also present. Western

red cedar and ponderosa pine appear occassionally on extremely wet or

dry sites, respectively. Twinflower (Linnaea borealis), snowberry,

and white spirea are common shrubs in this type. Sweetscented bedstraw

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triflorum), heartleaf arnica, starry Solomon's seal

(Smilacina stellata), and pinegrass also occur in the understory.

9) The alpine fir (Abies lasiocarpa) series of habitat types

is represented on approximately 3.7 percent of the study area (Fig.

4). The potential understory dominant is difficult to determine

because the area burned in 1945 and no old growth stands are present.

Young Douglas-fir are the most abundant trees with evergreen ceonothus,

serviceberry, and buffalo berry (Shepherdia canadensis) the dominant

shrubs. Pinegrass and kinnikinnick dominate the ground cover. The

alpine fir series is found above 5,200 feet (1,585 m) elevation.

Climatically this series is characteristic of areas having cold,

snowy, continental climates (Pfister et al. 1974).

10) The DF/Agsp-Rockland-Scree complex occurs on steep, southerly

slopes below 5,100 feet (1,554 m) elevation (Fig. 4). The DF/Agsp

habitat type constitutes approximately 75 percent of the complex while

rockland-scree makes up the remaining 25 percent. Plant species

present are those characteristic of the previously described individual

units of the complex.

11) The DF/Agsp-DF/Phma-Rockland-Scree complex is found on

approximately 1.6 percent of the study area. The three individual

units of the complex cover approximately equal areas. The plant species

present are those characteristic of the previously described individual

units of the complex.

12) The DF/Phma-Rockland-Scree-Douglas-fir/Rough fescue (DF/Fesc)

complex accounts for approximately 3 percent of the study area (Fig. 4).

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The three individual units of the complex cover approximately equal

areas. The plant species present on the DF/Phma and rockland-scree

portions of the complex are those previously described as characteris­

tic of these types. The DF/Fesc habitat type overstory on the study

area consists of large diameter Douglas-fir and ponderosa pine.

Rough fescue dominates the graminold cover with bluebunch wheatgrass,

prairie junegrass (Koleria cristata), and Idaho fescue also present.

Yarrow and arrowleaf balsamroot are conspicuous forbs. Shrubs

include bitterbrush, serviceberry, chokecherry, redstem ceonothus,

mountain maple, and ninebark.

Trapping

Trapping activities resulted in the capture of two bighorn sheep

on 14 July and five on 26 July 1975 (Table 3). Body weights were

not obtained for the animals captured on 26 July as they were released

immediately after the marking collars and eartags were in place. The

ambient temperature was above 95° F (35° C) and I felt capture stress

should be minimized.

Group Size and Age-Sex Composition

Between 1 January and 30 March 1976, 197 bighorn sheep groups

were observed, accounting for 1,103 sheep-observations (Fig. 5). Mean

group size was 5.6. Maximum, minimum, and mean group sizes for ewe-

juvenile, young ram, adult ram, and ewe-adult ram groups are listed

in Table 4. A t-test established a significant (p = .05) difference

in mean sizes of adult ram and ewe-juvenile groups. All of the ewe-

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Table 3. Age, sex, live weight, reproductive status of females, date of capture, and marking system for seven bighorn sheep captured during summer 1975.

Collar*

Capture Reprod. Pendant Flagging Ear Tags Date Sex Status^ Age Weight

113 bl. RBGG/y A0530 7-14-75 F NL 1 115 A0531

31 br. GBRG/w A0532 7-14-75 M — 1 100 A0533

112 bl. RRWG/y A0534 7-26-75 F NL 1 _ A0535

27 br. RBRG/w A0537 7-26-75 M - Lamb - A0538

Ill bl. GGWW/y AQ541 7-26-75 FL 2 — A0542

109 bl. RGGR/y A0544 7-26-77 F L 4 - A0545

117 bl. RWGG/y A0576 7-26-75 F NL 4 — A0577

^Color codes are as follows

bl. - black pendant W - white flag br. - brown pendant R - red flag w - white rope B - blue flag y - yellow rope G - green flag

’NL - non-lactating L - lactating

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o

\ ' ' ::'-"-:V///// / / ' ;

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Table 4. Minimum, maximum, and mean group size of bighorn sheep on winter range.

Group Size

No. Groups Group Type Observed Minimum Max imum Mean

Ewe-Juvenile 158 1.0 18.0 5.4

Young Ram 8 1.0 4.0 2.1

Adult Ram 27 1.0 16.0 7.0

Ewe-Adult Ram 4 2 20 10.3

All Categories 197 1.0 18.0 5.6

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adult ram groups were observed on or before 20 January 1976. The

largest ram group was observed on 19 January and consisted of 12 males

with horns 3/4 curl or longer, 2 males with horns 1/2 to 3/4 curl,

and 2 male yearlings. The largest ewe-juvenile group was observed

on 2 March and consisted of 6 lambs, 2 male yearlings, and 10 adult

ewes (includes female yearlings).

All animals present were classified according to sex and age in

149 of the bighorn sheep group observations (Table 5). To eliminate

possible bias, the groups that were not entirely classified were

excluded from the age and sex composition analysis.

Movements and Home Range

Standard diameters (Table 6) and minimum home range sizes

(Table 7) were calculated for nine marked bighorns. The female

yearling was observed three times during the winter. All other marked

animals reported were observed a minimum of four times each during

the winter. Eleven observations of an adult ewe was the maximum

number of reslghtings. Minimum home ranges of two adult males are

illustrated in Fig. 6. Figs. 7 and 8 illustrate minimum home ranges

of two adult females. The minimum home range of a male yearling is

illustrated in Fig. 9.

Availability Sample of the Study Area

The accuracy of the study area availability sample was tested

by comparing the random point predictions with polar planimeter

measurements of three mappable habitat categories. Results of this

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Table 5. Sex and age classification of bighorn sheep on winter range^.

Number Calculated Number: Observed 100 Adult Ewes^

Lambs 241 92

Yearling Male 54 21

Young Ram ( ^ 1/2 <3/4 Curl) 79 30

Adult Ram ( ^ 3/4 Curl) 99 38

Adult Females and Yearling Females 317

Yearling Females - 21

Total Yearlings — 42

Total Males ( > 1/2 Curl) 178 68

Sample Size 790

&Data includes only those group observations in which all animals were classified.

^Yearling females were assumed to equal yearling males, hence corrected adult females - 263.

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Table 6. Activity ranges of marked bighorn sheep during winter as determined by standard diameters.

Mean Range of Individual Classification Std. Dia. Sample Std. Dia. ml/km Size mi/km

Lamb 2.60/4.18 1 —

Male Yearling 4.65/7.48 1

Female Yearling 5.88/9.46 1 -

Adult Female 2.63/4.23 4 1.55-3.95/2.49-6.35

Adult Males 1.89/3.04 2 .67-3.10/1.07-4.98

Table 7. Minimum home ranges of marked bighorn sheep during winter.

Mean Size Sample Range Classif ication ac/ha Size ac/ha

Lamb 139/56.2 1 —

Male Yearling 726/243.8 1 —

Female Yearling 114/46.1 1 -

Adult Female 320/129.5 4 30-923/12.1-373.5

Adult Male 271/109.6 2 56-486/22.6-196.6

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N. I " f ^ "O CD

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8 ci'

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SC*IE IN Miifs "O CD

C/) SC*lt IN KUO«t^Efii C/)

tig. 6. Minimum winter home ranges of adult males No.. 415 ..d 427. ....wring 4,0 .cr., (1,8 b.) and ,6 respectively. a ’3 j I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11

.2>

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. [C

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59

comparison are given in Table 8. There was no significant difference

(p = 0.05) between the acreages as measured and the acreages as

predicted by the random point data.

Habitat Selection and Use

Chi-square goodness of fit tests established that the seven

general habitat factors tested were not used in proportion to their

occurrence on the study area (p - 0.005).

Elevation. Elevations below 4,800 feet (1,463 m) were used in

approximately the same proportion as their availability (Table 9).

Elevations above 4,800 feet (1,463 m) were avoided. Percentages of

bedding and feeding at various elevations are shown in Fig. 10. The

percentages of each activity were nearly equal at all elevations.

Topographic position. Wintering bighorns on the study area

avoided drainage bottoms and upper slopes (Table 10). Cliffy areas

were preferred while lower slopes, middle slopes, and ridges were

used in proportion to their availability. Percentages of bedding and

feeding sites on various topographic positions are shown in Fig. 11.

Middle and lower slopes received the highest percentages of feeding

activities. Percentages of bedding activities were highest on middle

slopes and cliffs.

Slope steepness. Areas with a slope steepness of 10-35 percent

were avoided by bighorn sheep (Table 11). Areas with a slope steep­

ness greater than 80 percent were preferred. Feeding activities were

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Table 8, Comparison of areas measured with polar planimeter versus areas predicted by random point sample.

Random point Measured Prediction Habitat factor Chi^

% acres % acres

^ 2800 ft. elev. 16.1 659 16.8 689 1.31

2810-3200 ft. elev. 15.5 638 15.0 615 .86

slope > 80 percent 8.9 367 8.2 336 2.86

Total = 5.03*

^Table = 5.99, p = .05 , 2 d.f.

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■O CD Table 9. Total bighorn sheep use at various elevations compared to availability of those elevations on the winter range. (/)C/) 3o" 2, Proportion of Proportion of Confidence interval CD Total study area group obser­ Expected on proportion of group 8 Elevation acreage in each vations in Number of number of observations (90% Apparent (feet above estimate category^ each category groups groups family confidence selection (5' sea level) ac/ha (Pa) observed behavior^ 2 (Po) observed coefficient) i3 CD 2800 690/279 .168 .234 46 33.1 .159 Po .263 None

c 2810-3200 616/249 .150 .193 38 29.6 .123 Po .263 None p. 3210-3600 677/274 .165 .223 44 32.5 .149 Po .297 None ■oCD 3610-4000 468/189 .114 .173 34 22.5 .106 Po .240 None Ic a 4010-4400 456/185 .111 .086 17 21.9 .036 Po .136 None o 3 ■o 4410-4800 403/163 .098 .066 13 19.3 .022 Po .110 None o 4810 792/321 .193 .025 5 38.0 .000 Po .053 Avoidance Q.CD Totals 4102/1660 197 196.9 cO ■o CD Proportions of total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred in each habitat in exact proportion to availability. (/) ^Calculated by multiplying proportion Pa x (total number of group observations); i.e., .168 x 197 = 33.1

^Pa confidence interval on Po = Preference; Pa confidence interval on Po = Avoidance; Pa within confidence interval on Po » None. ■DCD O Q. C g Q.

■D CD

C/) C/)

60 8 ^ Bedding Feeding (O' 50

40

3. H 3 " 3 CD S 30 CD ■D g O fXi Q. C a 20 3o "O o 10 CD Q.

■D CD 2400-2800 2810-3200 3210-3600 3610-4000 4010-4400 4410-4800 24810 (732-853) (856-975) (978-1097)(1100-1219)(1222-1341)(1344-1463) ($1466) C/) C/) ELEVATION (feet (m) above sea level)

Fig. 10. Percentages of bighorn sheep group bedding and feeding sites at various elevations. S’ ■o o Q. C g Q. Table 10. Total bighorn sheep use on topographie position categories compared to availability of those categories on the winter range. ■o CD

C/)w Proportion of Proportion of Confidence Interval 3o' study area group obser­ Expected on proportion of group O Total in eachg vations in Number of number of observations (90% Apparent S' Topographic acreage category each category groups groups family confidence selection CD position estimate (Pa) (Po) observed observed coefficient) behavior^ 8 3 ë' Drainage bottom 370/150 .090 .010 2 17.7 .000 Po .027 Avoidance i3 CD Lover slope 1108/448 .270 .218 43 53.2 .147 Po .289 None C 3. 3 " Middle CD slope 1026/415 .250 .330 65 49.3 .249 Po .411 None CD ■o Upper IC a slope 1043/422 .254 .122 24 50.0 .066 Po .178 Avoidance o 3 Ridge 403/163 .098 .127 25 19.3 .052 Po .202 None ■o o Cliff 152/62 .037 ,193 38 7.3 ,125 Po .261 Preference Q.CD Totals 4102/1660 197 196.8

■o CD ^Proportions of total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred in each habitat category in exact proportion to availability, C/i o' 3 ^Calculated by multiplying proportion Pa x (total number of group observations); i.e., ,090 x 197 = 18. 40 %" dding Feeding

30 g i i 20 PL, wllA A wEt tX X 10 I XX \XX# A / W 0 II Drainage Lower Middle Upper Ridge Cliff Bottom Slope Slope Slope

TOPOGRAPHIC POSITION

Fig. 11, Percentages of bighorn sheep group bedding and feeding sites on various topographic positions.

50

40

g 30

ëW cu 20

10

j s m . 0-10 10-35 35-60 60-80 >80

PERCENT SLOPE

Fig. 12. Percentages of bighorn sheep group bedding and feeding sites on various degrees of slope steepness.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■aS’ Q.o c gQ.

■o CD

C/i Table 11. Total bighorn sheep use on various categories of slope steepness compared to availability of those categories on the o' 3 winter range. O

CD 8 Proportion of Proportion of Confidence interval Total study area group obser­ Expected on proportion of group (5- 3" Slope acreage in each vations in Number of number of observations (90% Apparent steepness estimate category^ each category groups groups family confidence selection i (percent) ac/ha (Pa) (Po) observed observed coefficient) behavior 3 CD -n c 0-10 66/27 .016 .015 3 3.1 .000-.035 None 3 " CD 10-35 755/306 .184 .036 7 36.2 .005-.067 Avoidance ■oCD O 35-60 1817/735 .443 .467 92 87.3 .384-.550 None Q. C g. 60-80 1144/463 .279 .345 68 55.0 .266-.424 None o 3 ■o 80 320/129 .078 .137 27 15.4 .080-.194 Preference o

Totals 4102/1660 197 197 s .

3o " 5. Proportions of total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred ■o in each habitat in exact proportion to availability. CD ^Calculated by multiplying proportion Pa x (total number of group observations); i.e.» .016 x 197 = 3.1 C/iœ d 3 -Pa confidence interval on Po = Preference; Pa confidence interval on Po = Avoidance; Pa within confidence interval on Po « None. 66

concentrated on areas of 35-80 percent slope (Fig. 12). The highest

percentage of bedding activities was on 35-60 percent slopes.

Aspects. East and southeast aspects were avoided during the

winter (Table 12). South aspects were preferred while no selection

behavior was apparent for other aspects. Feeding and bedding site

percentage of bedding was over twice the percentage of feeding on

west slopes. Northwest, north, northeast, and east slopes received

light feeding use and no bedding use (Fig. 13).

Distance from steep terrain. Areas within 0.2 mile (322 m) of

a steep terrain area greater than 4 acres (1.6 ha) with greater than

80 percent slope were preferred (Table 13). Areas farther than 0.20

mile (322 m) from steep terrain were avoided. Percentages of bedding

and feeding at various distances from steep terrain were nearly equal

(Fig. 14).

Plant cover type. Shrubland-grassland and open forest plant

cover types were preferred by bighorn sheep during winter (Table 14).

Closed forest was avoided and rockland was used in proportion to its

availability on the study area. The percentage of bedding sites on

rockland was nearly three times the percentage of feeding sites

(Fig. 15). The percentage of feeding sites in open forest was sub­

stantially higher than the percentage of bedding sites. Percentages

of total use on areas of 0-24, 25-75, and 76-100 percent coniferous

canopy cover were 59, 40, and 1, respectively.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 "DCD O Q. C g Q.

■o CD

C/) o' Table 12. Total bighorn sheep use on various aspects compared to availability of those aspects on Che winter range. Z 5 2,

CD Proportion of Proportion of Confidence interval 8 Total study area group obser­ Expected on proportion of group acreage in each vations in Number of number of observations (90% Apparent cB' estimate category^ each category groups groups ^ family confidence selection s Aspect ac/ha (Pa) (P^ observed observed coefficient) behavior^ i3 CD Northwest, North, and c p. Northeast 49/20 .012 .005 1 2.4 0.00 Po .017 None East 336/136 ,082 ,015 3 16.2 0.00 Po .036 Avoidance ■oCD O Southeast 673/272 .164 .066 13 32.3 .023 Po .109 Avoidance Q.C a South 1026/415 .250 .503 99 49.2 .417 Po .589 Preference 3o ■o Southwest 1665/674 .406 .330 65 80.0 .249 Po .411 None o West 353/143 .086 .081 16 16.9 .034 Po .128 None

CD Q. Total 4102/1660 197 197.0

"3 Proportions of total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred in each habitat CD category in exact proportion to availability.

C/) ^Calculated by multiplying proportion Pa x (total number of group observations); i.e., .012 x 197 * 2,4, o' 3 *^Pa confidence interval on Po » Preference; Pa confidence interval on Po * Avoidance; Pa within confidence interval on Po « None* Bedding 1^^ Feeding

50

40

Ë 30 M O m S P-i 20

10 W

m

N,NW,NE SE sw w

ASPECT

Fig. 13 . Percentages of bighorn sheep group bedding and feeding sites on various aspects.

60 —

50

40

§ u 30 Pi w P-. 20

10

.00-.10 .11-.20 .21-.30 .31-.40 %.41

DISTANCE TO STEEP TERRAIN (miles)

F i g . 14 Percentages of bighorn sheep group bedding and feeding sites at various distances to steep terrain.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 ■OCD O Q. C S Q.

% Table 13. Total bighorn sheep use at various distances from steep terrain compared to availability of areas at chose distances on the C/î winter range. o*3 2,

CD Proportion of Proportion of Confidence interval 8 Total study area group obser­ Expected on proportion of group Distance from acreage in each vations in Number of number of observations (90% Apparent â' steep terrain estimate category® each category groups groups family confidence selection (miles) ac/ha (Pa) (Po) observed observed coefficient) behavior'^ i3 CD O-.IO (0-.16 km) 1329/538 .324 .558 110 63,8 .475 Po .641 Preference C .11-.20 (.18-.32 km) 624/253 .152 .259 51 29.9 .186 Po .332 Preference ■oCD O .21-.30 Q. C (.34-.48 km) 722/292 .176 .066 13 34.7 .025 Po .107 Avoidance a o 3 .31-.40 "O (. 50-.64 km) 656/265 .160 .086 17 31.5 .039 Po .133 Avoidance o .41 CD ( .66 km) 771/312 .188 .030 6 37.0 .002 Po .058 Avoidance D.

Oc Total 4102/1660 197 196.9 ■o CD Proportions of total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred in each cn habitat in exact proportion to availability. o' 3 ^Calculated by multiplying proportion Pa x (total number of group observations); i.e., .324 x 197 = 63.8.

^Pa confidence interval on Po = Preference; Pa confidence interval on Po = Avoidance; Fa within confidence interval on Po = None, ■o I I

■o CD

inw o’3 Table 14. Total bighorn sheep use on various plant cover types compared to availability of those types on the winter range. O

CD 8 Proportion of Proportion of Confidence interval Total study area group obser­ Expected on proportion of group cq’ Plant acreage In each vations in Number of number of observations (90% Apparent 3" cover estimate category® each category groups groups family confidence selection i type ac/ha (Pa) (Po) observed observed coefficient) behavior‘s 3 CD Rockland 554/225 .135 .137 27 26.6 .082 Po .192 None

3. Shrubland 3" CD and Shrubland- CD ■D Grassland 1296/524 .316 .4^ 90 62.3 .377 Po .537 Preference O Q. C Open g o Forest 1058/428 .258 .396 78 50.8 .318 Po .474 Preference 3 -o Closed o Forest 1194/483 .291 .010 2 57.3 .000 Po .026 Avoidance

& Total 4102/1660 197 197.0

o c ^Proportions of total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred In each % habitat in exact proportion to availability. ^Calculated by multiplying proportion Pa x (total number of group observations); i.e., .135 x 197 = 26.6. cn CO o' 3 “^Pa confidence interval on Po = Preference; Pa confidence interval on Po = Avoidance; Pa within confidence interval on Po = None. 60 Bedding Feeding

50

40

S 30 Pi W PU 20

10

0 iwj «*i«<&jQ535L Rockland Shrubland Open Closed Forest Forest

PLANT COVER TYPE

Fig. 15. Percentages of bighorn sheep group bedding and feeding sites in various plant cover types.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72

Habitat type. The rockland and scree habitat type classification

was preferred by wintering bighorn sheep (Table 15). The DF/Phma

habitat type was avoided. Percentages of bedding and feeding sites

occurring on various habitat types is shown in Fig. 16. Rockland

and scree and the DF/Syal/Syal types received the highest percentages

of feeding use. The highest percentages of bedding activities were

on rockland and scree and DF/Agsp-rockland and scree habitat types.

Comparison of Habitat Use by Group Types

Use of various habitat factors by young ram, adult ram, and ewe-

juvenile groups is compared in Table 16. T-test results indicated

adult ram groups were observed at a significantly (0.001) higher mean

elevation than young ram or ewe-juvenile groups. Eighty-one percent

of the adult ram groups were observed above 3,600 feet (1,097 m)

elevation while 72.1 percent of ewe-juvenile observations were below

3,600 feet (1,097 m) (Table 16). There was a significant (0.01)

difference in mean distance to the nearest 15-foot-minimum (4.6 m)

cliff, adult ram groups occurring^closer than ewe-juvenile or young

ram groups. In contrast, adult ram and ewe-juvenile groups were

sighted in areas more than 0.3 miles (483 m) from steep terrain ( 80

percent slope, 4 ac (1.6 ha) minimum size) 22.2 and 8.9 percent of the

time, respectively. Adult ram groups utilized ridges and upper slopes

a greater percentage of the time than young ram or ewe-juvenile groups

did. The DF/Agsp-rockland and scree habitat type complex was used a

much greater percentage of the time by adult ram groups than other

group types were.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■o oû. c Table 15. Total bighorn sheep use un various forest habitat types compared to availability of those types on the winter range. 8Û.

■O CD Proportion of Proportion of Confidence Interval Total study area group obser­ Expected on proportion of group forest acreage in each vations in Number of number of observations (90% Apparent C/)W o" habitat estimate category® each category groups groups ^ family confidence selection 3 types ac/ha (Pa) (Po) observed observed coefficient) behavior*" 5 CD Rockland 8 and Scree 1243/503 JW3 .4M 97 5M7 .402-.582 Preference 5 (§■ DF/Agsp- 3" Rockland i and Scree 472/191 .115 .U8 35 22^ .109-.247 None 3 CD DF/Agsp- DF/Phma- Rockland 3. and Scree 66/27 .016 .025 5 3.2 .000-.053 None 3" CD DF/Phma- CD "O DF ,'fesc- O Rockland Q. C and Scree 120/48 .029 .030 6 5.7 .000-.061 None a O 3 EF/Syal/ "D Syal 538/218 .131 .162 32 25.8 .096-.228 None O DF /Pima 1346/545 .328 .081 16 64.6 .032-.130 Avoidance CD Q. PP/Putr 17/7 .004 .020 4 0.8 .000-.045 None

O .All other C types^ 300/121 .M3 .01 2 14.4 .000-.028 Avoidance -O CD Total 4102/1660 197 196.9 (gC/) o' 3 ^Proportions cf total study area represent expected bighorn sheep group observation values as if bighorn sheep occurred in each habitat in exact proportion to availability.

^Calculated by multiplying proportion Pa x (total number of group observations); i.e., .303 x 197 = 59.7.

cPa confidence interval on Po = Preference; Pa confidence interval on Po * Avoidance; Pa within confidence interval on Po - None.None, d Collective category contains AF, DF/Agsp, DF/Caru, GF/Clun/Clun, DF/Spbe habitat types. ■OCD O Q. C g Q.

60 Bedding Feeding “D CD

WC/) o" 3 50 O

8 40 ci'

H § 30 M 3 w 3" Pm CD

CD "O O 20 Q. O 3 ■O O IQ

CD Q. 0 ■O Rockland- DF/Phma DF/Syal PP/Putr Complex Complex Complex All Other CD Scree C^ Types C/) C/) FOREST HABITAT TYPE

Fig. 16. Percentages of bighorn sheep group bedding and feeding sites on various habitat types.

^DF/Agsp-Rockland-Scree ^DF/Agsp-DF/Phma-Rockland-Scree ^DF/Phma-DF/Fesc-Rockland-Scree 75

Table 16. Comparisons of habitat use by ewe-juvenile, young ram, and adult ram bighorn sheep groups.

Group Type

Habitat factor Ewe-juvenile Young ram Adult ram

Moan distance CO nearest conifer (feet) 57 .6 46.3 43.0

Mean elevation 3333 3073 4231

Mean distance to 15-foot-minlmum cliff (feet/meters) 132/40,2 101/30.8 50/15.2

Percentages of observations at various elevations 2800 feet 25.9 37.5 7.4 2810-3200 feet 20.9 37.5 3.7 3210-3600 feet 25.3 12.5 7.4 3610-4000 feet 17. 1 0 22.2 4010-4400 feet 7.6 12.5 14.8 4410-4800 feet 3.2 0 25.9 4800 feet 0 n 18.5

Percentages of observations at various distances from steep terrain ( 80% slope, 4 ac (1.6 ha) minimum size) .1 miles 57.6 73.0 40;7 .11-.20 miles 26.6 12.5 29.6 .21-.30 miles 7.0 0 7.4 .31-.40 miles 7.6 0 11.1 .41 miles 1.3 12.5 11.1

Percentages of observations on various topographic positions Drainage bottom .6 12.5 0 Lower slope 26.6 12.5 0 Middle slope 34.8 25.0 14.8 Upper slope 10.8 0 25.9 Ridge 9.5 12.5 33.3 Cliff 17.7 37.5 25.9

Percentages of observations on various degrees of si ope steepness 0-10 percent 0 0 10-35 percent 14 9 35-60 percent 45 57 63 60-80 percent 37 29 14 80 percent 14 0 14

Percentages of observations on various aspects Northwest. North, and Nurtheaut . 6 0 0 Eas t 1.3 0 3.7 Southcas t 4.4 0 22.2 South 53.2 50.0 33.3 Southwes t 35.4 25.0 22.2 West 5.1 25.0 18.5

Percentages of observations on various plant cover types Rockland 15.2 0 7.4 Shrub land 44.9 37.5 51.8 Open forest 39.2 t>2.5 37 .0 .6 Closed For est .6 0

Percentages of observations on various forest habitat types Rockland and Scree 54 63 15 DF/Agsp-Rockland and Scree 11 12 65 DF/Syal/Syal 18 25 4 DF/Phma 8 0 12 DF/Spbe 1 0 4 OF/Agap-DF/Phma-Rockland and Scree 3 0 0 Dl'/Phm.i-nF/F.'UC-Rock land and Scree 3 I) 0 PP/i'ijtr 0 Ü

local number ot group observ.r tlons 158

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76

Darometrie Pressure and Température

The temperature records' from the thermographs at 2,700 feet

(823 m) and 4,300 feet (1,311 m) are illustrated in Figure 17. The

barometric pressure record for the corresponding peri od is included

in the figure.

Habitat Use Related to Meteorological Conditions

The only non-triviaJ Pearson correlation coefficients for meteor­

ological variiibles versus possible dependent variables at a signifi­

cance level of 0.01 were barometric pressure versus elevation (r = -.206,

n = 195) and barometric pressure versus distance to the nearest 15-foot-

minimum (4.6 m) cliff (r = 0.167, n - 195). Significant (0.05) variation

in mean elevation and mean distance to nearest 15-foot-minimum cliff

during periods of low, medium, and high barometric pressures were

revealed by analysis of variance (Table 17). Mean group size exhibited

significant (0.05) variation during periods of decreasing, relatively

stable, and increasing barometric pressure (Table 18).

Mean elevation of 44 group oljservations during temperature inversion

conditions was 3,640 feet (1,109 m) while mean elevation of 153 observa­

tions during non-inversion conditions was 3,402 feet (1,037 m). A t-test

established that this was a significant (0.05) difference.

hue to mild winter conditions, snow cover was entirely absent below

5,100 feet (1,554 in) elevation during, most of the winter. Above this

elevation, adult ram groups were observed to avoid fresh snow in excess

of approximately 18 inches (46 cm). When melting, and refreezing

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD O Q. C g Q. XW) ■D • 3L40 CD 30.95 C/) C/) X w

w P- 29.60 8 10 ci' 2700 feet (823 m) 4300 feet (1311 ta)

3 3" CD ■DCD O Q. C a 3O "O O

CD Q.

■D CD -10

C/î C/)

-15

JANUARY FEBRUARY MARCH

Fig. 17. Barometric pressures (top) and temperatures at two elevations (bottom) during the study period, 78

Table 17. Mean elevation and mean distance to the nearest 15-foot- minimum (4.6 m) cliff of bighorn sheep groups during low, medium, and high barometric pressures.

Mean distance Number Mean nearest of eleva t ion cliff obser­ barometric Pressure (feet/m) (feet/m) vations

Low ( 30.38 in. llg) 3621/1104 87/27 62

Medium (30.39-30.59 in. tig) 3422/1043 116/35 68

High ( ^ 30.60 in. Hg) 3334/1016 158/48 67

Table IS. Coniparison of bighorn sheep mean group size during periods of decreasing, relatively stable, and increasing barometric pres s u re.

Mean Number of Barometric Pressure Trend group obs er- (previous 4 hours) s i ZG vations

Decreasing ( < -.005 in. Ilg gain/hr) 4.64 61

Relatively stable (-.005 to .005 in. Hg gain/hr) 6.26 73

Increas.ing ( > .005 in. Hg gain/hr) 5. 73 63

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79

created crust characteristics that resulted in sheep track depths

of 2 inches (5 cm) or less, some use of snow covered areas was noted.

Bedding Site Characterization

During the study, 189 bedding sites wore categorized as night

beds or day beds. Table 19 provides a comparison of various habitat

characteristics associated with day and night bedding sites. In

general, night bedding sites were closer to cliffs and in areas of

greater conifer density than day bedding sites were.

Fecal pH

The difference in mean fecal pH values for bighorn sheep and mule

deer shown in Table 20 was significant (p = 0.05) by a t-test.

However, the large amount of overlap in pH values prevented the

development of fecal pellet differentiation guidelines based on pH.

Fecal Group Counts Related to Site Factors

For all statistical analyses of fecal pellet plot data, the three

different sampling areas (lower slope, upper slope, and ridge) were

treated separately. Fecal group frequency distributions were compared

with a theoretical Poisson distribution (Loveless 1967). A Poisson

distribution requires that the probability of containing a fecal group

is small and constant for all plots. The results of chi-square tests

of goodness of fit are shown in Table 21. This evidence suggests

random distribution of fecal groups on lower slopes and ridges. Mean

fecal groups per plot were 2.45, 1.0, and 0.88 for the ridge, upper

slope, and lower slope samples, respectively.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 -OCD O Q. C g Q. Table 19. Comparison of habitat characteristics associated with day bed sites and night bed sites. -g (/) o'3 Day Bed Sites Kight Bed Sites 2,

CD 8 Characteristic Minimum Maximum Mean Minimum Maximum Mean

(S' 3 Distance to cliff i3 CD (feet) 1 200 12.5 3 300 73

C p. Conifer canopy cover 3" CD (percent) 0 86 21 6 95 63 -oCD O Conifer density Q. C (Stems/acre) .4 76 17 7 155 22 g. o 3 "O Conifer basal area o (f t^/acre) 0 93.3 20.9 8.3 127.2 26.6

CD Q. Average distance to closest conifer (feet) 8 155 63 1 26 9

"O CD Sample Size 121 68 (/) o’ 3

00 o 81

Table 20. Comparison of winter fecal pH values of bighorn sheep and mule deer.

Species Mean S.D. 95% C.L. Range

Bighorn sheep 6.92 .15 ±.04 6.58-7.30

Mule deer 6.85 .16 ±.05 6.44-7.25

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82

Table 21. Observed fecal group frequency distributions compared with theoretical Poisson probabilities.

No. of pellet Poisson Sampling groups/ Observed expected area^ plot frequency f requency

Lower slope ob 48 45.69 .117 1 29 31.00 . 129 2 9 10. 51 .217 3—4 4 2.80 .514 Total = .977^

Upper slope 0 9 15.45 2.69 1 26 15.45 7.20 2-4 7 11.10 1.51 Total = 11.4Qd

Ridge 0 13 6.54 6.38 1 15 16.01 . 06 2 15 19.62 1.09 3 12 16.02 1.01 4 11 9.80 .15 5-11 9 8.01 .12 Total = 8.81^

^Sample size is 90 on lower slope, 42 on upper slope, and 76 on ridge sampling areas.

^The mean number of pellet groups per plot was 0.678 for the lower slope, 1.00 for the upper slope, and 2.45 for the ridge sampling areas.

*“Pellet groups were randomly distributed within this sampling area (p = 0.05).

‘^Pellet groups were not randomly distributed within this sampling area (p = 0.05).

^Pellet groups were randomly distributed within this sampling area (p = 0.05).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 83

Pearson correlation coefficients (Mendenhall 1971) were calculated

for fecal group ci.ntnts per plot versus elevation, distance to the

nearest 15-fout-Min imum cliff (4.6 m) , distance to the nearest conifer,

conifer canopy coverage, and conifer density (stems/acre). Correlation

coel 1 icients at s J p.n i f j cane e levels < 0.05 are reported in Table 22.

Distance to the nearest cliff was negatively correlated (fewer pellet

groups at greatei- distances from cliffs) with pellet group counts on

all three saMjrl ing areas. Distance to the nearest conifer was negatively

correlated with fecal group counts on lower slopes. In the ridge sample,

elevation was positively correlated with fecal group counts.

Kendall rank order correlation coefficients (Nie et al. 1975) were

calculated for fecal group counts per plot versus total g raminoi d cover,

total shrub cover, and canopy coverage classes for all individual shrub

species. Correlation coefficients at significance levels < 0.05 are

reported in Talilc 22. The highest correlation obtained (0.56) was for

total graminoid cover on lower slopes.

Food Habits

Microhistological analysis of fecal material found bluebunch

wheatgrass to have the highest percent relative density of any plant

species (Table 23). (Irani inoids constituted 38.01 percent of the winter

fecal material, trees and shrubs constituted 51.38 percent, and forbs

10.60 percent. Mountain maple and serv iccherry oi tairred most often in

the browse class and yarrow was the most abundant forh species in winter

fecal pellets.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■oCD 0 Q. 1 Table 22. Relationships of fecal group locations^ to various site factors,

(/)(g Pearson Kendall o'3 Sampling correlation correlation area Site characteristic coeff icient coefficient

Lower slope Distance to nearest cliff -.18* Distance to nearest conifer -.22* Total graminoid cover .56*** Bitterbrush canopy cover .25* Rabbitbrush canopy cover .19** 3 Total shrub cover .21* 3" CD

CD Upper slope Distance to nearest cliff -.18* "O Total graminoid cover a.O c Mockorange canopy cover -.36 g o Evergreen ceonothus canopy cover .32* 3 "O o Ridge Distance to the nearest cliff -.39*** Elevation .27** CD Q. Serviceberry canopy cover -.20* Rabbitbrush canopy cover .19* Oc Evergreen ceonothus canopy cover .21* ■o CD

(/) ^The number of plots included 90 on the lower slope, 42 on the upper slope, and 76 on the o' 3 ridge sampling areas.

*P 0.05

0.01 00 0,001 85

Table 23. Percent relative densities of plant species in bighorn sheep fecal pellets deposited during winter 1975-76.

Mean Range Freq. %

Grasses and grasslike plants Agropvron spicatum 29.37 12.,43-49.33 100 Elymus spp. 3.10 0 - 6.95 80 Festuca spp. 1.84 0 - 5.66 50 Koleria cristata .11 0 - 2.28 5 Stipa spp. 1.78 0 - 5.62 55 Carex spp. 1.81 0 - 6.18 60 Total 38.01

Forbs Achillea millefolium 4.06 0 -10.82 90 Artemesia frigida .22 0 - 2.49 10 Castillej a sp. 2.82 0 -10.32 70 Draba sp. .34 0 - 4.51 10 Penstenon spp. .15 0 - 3.01 5 Townsendia sp. 1.39 0 - 4.77 40 Unknown compositae .28 0 - 5.66 5 Unknown forb 1.34 0 - 5.25 50 Total forbs 10.60

Trees and shrubs Acer glabrum 11.46 2,.28-16.28 100 Amelanchier alnifolia 11.02 4,.77-17.97 100 Mahonia repens 1. 44 0 - 5.30 45 Ceanothus spp. 6.32 0 -15.82 95 Chrysothamnus nauseosus 1.93 0 - 5.87 65 Juniperus spp. 1.83 0 - 6.14 65 Pinus ponderosa . 64 0 - 6.97 15 Prunus virginiana 2.73 0 -13.04 70 Pseudotsuga menziesii 8.21 3 .41-13.83 100 Purshia tridentata 5.52 0 -13.85 85 Ribes spp. .28 0 - 2.2 15 Total trees and shrubs 51.38

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86

Forage Utilization

Estimated average forage utilization for five plant species on the

winter range is shown in Table 24. Mountain maple had the highest

utilization of the browse species. The linear regression equation

utilized to estimate the percent utilization by weight of bluebunch

wheatgrass was: log (% weight removed) = 0.027 (% height removed) -

0.44529. The r^ value for this relationship was 0.9256 for percent

height removed values of 10-90 percent. Forage utilization was greater

above 3,800 feet (1,158 m) for all five plant species.

Competition

The only other wild ungulates observed on the winter range were

five groups of mule deer, totalling 19 animals. They were observed on

shrubland-grassland cover types at a mean elevation of 4,460 feet

(1,359 m). The remains of a 2.5 year old white-tailed deer, apparently

killed by a mountain lion (Felis concolor), were discovered on

7 February 1976. Bone marrow condition indicated no evidence of stress.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■o I I Table 24. Estimated average utilization for five forage species on the winter range.

(/> Shrubs Grass o'3

% twigs % length % weight 8 Elevation Species browsed removed removed S' Less than 3800 feet (1158 m) Araelanchier alnifolia 69 31 Acer glabrum 78 51 - Purshia tridentata 56 — - Prunus virginiana 72 -— 3.3“ CD Agrop-yron spicatum — *- 30 "OCD O More than 3800 feet (1158 m) Amelanchier alnifolia 88 - Q. C Acer glabrum 96 - g - - o3 Purshia tridentata 85 "O Prunus virginiana 94 -- o Agropyron spicatum 55

CD Q.

OC %

C/Î o' 3

CO CHAPTER V

DISCUSSION

Trapping

Bighorn sheep readily became habituated to the salt-baited

portable corral trap during summer. In late July and early August,

as many as 25 sheep were observed in the open trap at one time.

Major disadvantages of the corral trap were the necessity for two or

more people to handle the collaring operations and the injury hazard

to lambs (1-4 months of age) before they could be removed to a

holding pen. The hand-operated triggering device, which consisted

of a rope holding the gates open and tied to a tree, operated

satisfactorally with no injury to the sheep.

Large corral type traps have been used successfully for capturing

bighorn sheep by various researchers (Hunter et al. 1946, Putman 1950,

Aldous et al. 1958). Erickson (1970) captured 68 Dali sheep (Ovis

dalli) at a natural mineral lick in 8 days utilizing a drop net.

Apparently many wild sheep populations are susceptible to relatively

efficient trapping techniques designed to capture many individuals

with each setting. Although the use of a corral trap baited with

salt was successful in the. Thompson Falls area, it is recommended that

winter trapping be attempted first. The vigorous escape attempts of

HS

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yearling and adult bighorns could result in the injury or death of

lambs only a few months old.

Group Size and Age-Sex Composition

The mean group size for all observations on the winter range was

5.6 (Table 4). Adult ram groups averaged 7.0 and ewe-juvenile groups

averaged 5.4. Oldemeyer (1966) reported a mean winter group size of

8.7 in Yellowstone National Park. Geist (1971) reported wintering

bighorns averaging 5.2 and 9.5 for male and female groups, respectively.

Blood (1963) reported that the mean winter group size of ewes was

greater than that of rams. The comparatively low mean winter group

size on the Thompson Falls study area may reflect the diverse nature

of the habitat and/or the mildness of the winter. Habitat character­

istics vary in repeating patterns on the study area. Selection

behavior would not be expected to result in large concentrations of

animals unless snow conditions restricted movements.

The age-sex composition data (Table 5) agree with Brown's (1974)

report that productivity was as great or greater than most other

bighorn populations reported (Buechner 1960:80). The yearling:ewe

ratio of 42:100 indicates low overwinter lamb mortality.

The male:female ratio of 68:100 (Table 5) is essentially identical

to the 71:100 ratio Brown (1974) considered his best estimate.

Oldemeyer (1966) reported a 78:100 maie;female ratio during winter in

Yellowstone National Park. Smith (1954) reported a 74:100 sex ratio

in Idaho. In contrast, Woodgerd (1964) reported males to outnumber

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females on Wildhorse Island, Montana. Differential mortality and/or

difficulty in observing one sex group could account for unequal

sex ratios. Cowan (1950), Smith (1954), Sugden (1961), and Moser

(1962) reported sex ratio biases due to the occupation of separate

ranges by rams and ewes. The occupation of higher elevations by ram

groups during winter (Table 16) on the Thompson Falls winter range

probably biased maletfemale ratios in favor of females.

Movements and Home Range

Mean standard diameters during winter were 2.63 miles (4.23 km)

and 1.89 miles (3.04 Ion) for adult females and adult males, respec­

tively (Table 6). Mean minimum home range size was less for adult

males than adult females (Table 7). Brown reported winter standard

diameters of 3.88 miles (6.2 km) and 2.20 miles (3.5 km) for lamb

and yearling males and lamb, yearling, and adult females, respectively.

Erickson (1972) reported standard diameters of 0.92 mile (1.5 km) for

males and 1.42 miles (2.3 km) for females during a severe winter.

It is apparent from the range of standard diameters and minimum home

ranges observed in this study (Tables 6 and 7) that individual differ­

ences existed within each sex group. A combination of winter severity

and strength of individual home range fidelity may determine the extent

of winter movements. Adult males may tend to restrict their movements

more during winter than adult females do.

Availability Sample of the Study Area

As pointed out by Marcum (1975), there is an Increased awareness

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of the need to relate the use of habitat categories by a given animal

species to the availability of those factors (Nicholls and Warner 1972,

Neu et al. 1974, Hirst 1975, and Peek et al. 1976). This requires

that the proportion of each habitat category of interest be determined.

When working with complex patterns of availability (i.e., plant

community mosaics and areas a certain distance from cliffs), the mapping

techniques often utilized would be extremely time consuming and diffi­

cult. The random point technique of sampling availability provided

a reasonably accurate (Table 8) and time-efficient alternative.

Habitat Selection and Use

The failure of wintering bighorn sheep to utilize the various

habitat categories tested in proportion to their availability is

similar to the findings of Shannon et al. (1975). They reported high

correlations between some habitat variables and numbers of bighorn

sheep observed on a British Columbia winter range. This suggests that

bighorn sheep are selective in their use of potential winter range.

Elevation. Bighorn sheep avoided portions of the winter range

above 4,800 feet (1,463 m) elevation (Table 9). They exhibited no

apparent preference or avoidance for other elevational categories. The

only permanent snow cover on southerly slopes within the study area

occurred above 5,100 feet (1,554 m) elevation. Shannon et al. 0-975)

and Stelfox (1975) reported a significant negative correlation between

snow depth and numbers of bighorn sheep observed. Oldemeyer (1971)

reported bighorn distribution to be affected by snow depth. lioness

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and Frost (1942), Smith (1954), Geist (1971), and Brown (1974) reported

that wintering bighorn sheep select snow free sites for feeding.

Honess and Frost (1942), Smith (1954), McGann (1956), Sugden (1961),

Moser (1962), Blood (1963), and McGullough and Schncegas (1966)

reported that bighorn sheep leave summer range in response to storms

and snowfall. The avoidance of snow cover and random use of snow free

portions of the study area would result in the observed pattern of

elevational distribution of bighorn sheep.

Topographic position. Bighorn sheep on the winter range avoided

drainage bottoms and upper slopes while exhibiting a preference for

cliffs (Table 10). Oldemeyer et al. (1971) reported that 75 percent

of the bighorn use during winter was on steep terrain and ridgetops,

with 14 percent of sightings occuring on rocky outcrops. Brown (197 4)

reported that 50 percent of his bighorn observations throughout the

year occurred on broken ridges, 43 percent on talus, and 7 percent on

rock outcrops. A close association between wild sheep and rugged

terrain has been reported by Couey (1950), Smith (1954), Flook (1962),

and Schallenberger (1965). McCann (1956) stated "the ecological niche

of the mountain sheep consists of temperate to subarctic conditions

which provide relatively continuous cliffy or broken topography." A

preference for rough terrain would account for the avoidance of

comparatively smooth drainage bottoms and preference for cliffs

observed in this study. The avoidance of upper slopes is more difficult

to explain. The most extensive cliff areas on the winter range are

above upper slopes. A lack of available forage due to the absence of

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stable islands of vegetation in the loose debris at the base of cliffs

may account for the light use of upper slopes.

Slope steepness. Wintering bighorn sheep avoided areas having

a slope steepness of 10-35 percent and preferred areas with a slope

steepness greater than 80 percent (Table 11). Shannon et al. (1975)

reported that bighorn sheep moved onto steep slopes in late winter.

They felt that use of slopes was related to associated abiotic or

biotic features rather than slope per se. The use pattern on slopes

of various degrees of steepness undoubtedly reflects, at least in part,

the previously discussed affinity of bighorn sheep for rough topography.

The absence of an apparent avoidance behavior toward areas with a 0-10

percent slope may be a result of random variation in the data. Only

1.6 percent of the study area was classified in the 0-10 percent slope

category.

Aspect. Bighorn sheep on the winter range avoided east and south­

east aspects and preferred south aspects (Table 12). Shannon et al.

(1975) reported a late winter bighorn sheep distribution favoring

southwest exposures. Oldemeyer (1966) reported that percent use on

south, southeast, southwest, west, east, and north exposures was 27, 0,

20, 29, 2, and 22, respectively. Constan (1967) reported bighorn winter

utilization of south, southeast, and southwest aspects as 18, 22, and

56 percent, respectively. McCann (1956) determined that east and

south facing slopes were used most heavily by wintering bighorn sheep

in the Gros Ventre Range of Wyoming. Flook (1962) stated that most

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bighorn winter ranges in Banff and Jasper National Parks, Alberta

have a southern exposure. He attributed this to the rapid dissipation

of snow by direct sunlight on those aspects.

Without corresponding availability data, aspect utilization

information is difficult to interpret. Since southern slopes in the

northern latitudes face the direction of the winter sun, they absorb

more radiant energy than other aspects (Moen 1973). A preference for

these southerly aspects by wintering ungulates is undoubtedly related

to this phenomenon. The absence of snow cover on most of the study

area during winter suggests that the heavy use of south slopes, in

this instance, was a response to microenvironmental, physical, or

biotic characteristics of south slopes ratlier than snow depth. The

utilization patterns reported by other investigators probably reflect

local winter range characteristics and varying degrees of winter sever­

ity.

Distance to steep terrain. Areas more than 0.2 miles (322 m) from

steep terrain (defined as areas greater than 4 acres (1.6 ha) with a

slope steepness greater than 80 percent) were avoided by wintering

bighorn sheep (Table 13). Areas within 0.2 miles (322 m) were preferred

Shannon et al. (1975) reported a significant negative correlation

between numbers of bighorn sheep and distance from "escape terrain"

during winter, spring, and summer. Oldemeyer et al. (1971) reported

that 86 percent of winter observations of bighorn sheep were less than

100 yards (91 m) from "escape habitat". The results from the present

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study are quite striking in that there were no 0.1 mile (161 m)

categories that were utilized in approximate proportion to their

availability (Table 13). There was a preference for lands 0.1-0.2

miles (161-322 m) from steep terrain and an avoidance of lands only

0.1 mile (161 m) farther from steep terrain. Bighorn sheep apparently

have a very strong innate preference for lands in close proximity to

steep terrain and will normally limit their activities to those areas.

Plant cover types. Shrubland-grassland and open forest plant

cover types were preferred by wintering bighorns and closed forest

was avoided (Table 14). Other plant cover types were used approximately

in proportion to their availability. Smith (1954) determined in an Idaho

study that percent winter use on open grass cover types was greater

than percent availability and percent use on browse cover types was less

than percent availability in Idaho. He reported that open timber and

cliff areas were used approximately in proportion to their availability.

Oldemeyer et al. (1971) reported percentages of winter bighorn use on

forest, grass, and shrub vegetative types were 13, 78, and 9, respec­

tively. Constan (1972) found winter use percentages of 2, 20, 9, and

69 on lodgepole pine, Douglas-fir, sagebrush, and bunchgrass vegetation

types, respectively. The preference for shrubland-grassland and open

forest on my study area may reflect the absence of large grassland

areas. Bluebunch wheatgrass is locally abundant and palatable shrubs

are common on slirubland and open forest cover types. A preference for

cover types containing the most forage would account for the observed

utilization pattern.

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The higher percentage of bedding sites than feeding sites on

rocklands reflects both lack of forage plants on rocklands and the

tendency for bighorns to bed in rocks on sunny winter days. The open

timber cover type received a higher percentage of feeding use than

bedding use. This may reflect a preference for day bed sites without

nearby conifers that would obstruct the view of the surrounding

terrain. This differential use of habitat for day time bedding and

feeding activities is in contrast to Smith's (1954) report that

bighorns selected day beds wherever they happened to be feeding.

Forest habitat types. Wintering bighorn sheep preferred rockland

and scree and avoided the DF/Phma habitat type (Table 15). Other

major habitat types were used in approximate proportion to their

availability. The apparent selective behavior of bighorn sheep in

regard to forest habitat types (potential climax communities) is most

readily explained in terms of the present physical and biotic charac­

teristics of the land. The rockland and scree habitat type classifi­

cation is currently vegetated by the rockland and shrubland-grassland

plant cover types. A preference by bighorn sheep for areas with cliffs,

steep slopes, and available forage probably accounted for the high use

of rockland and scree. A significant proportion of the DF/Phma habitat

type on the study area occurred at high elevations on east and southeast

aspects (Fig. 4). In addition, most of the DF/Phma habitat type was

occupied by a closed timber cover type. The association of these habitat

characteristics with the DF/Phma habitat type probably account for the

low level of observed use.

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Comparison of Habitat Use by Croup Type

Adult ram groups were observed at significantly (p = .001)

higher elevations than ewe-juvenile or young ram groups (Table 16).

Adult ram groups were never observed in close proximity to ewe-

juvenile groups after 20 January J976. Observations of separation

of bighorn sheep into sex groups have been reported by Couey (1950),

Smith (1954), Îloser (1962), blood (1963), and Geist (1971). Grubb

and Jewell (1966) observed ewe and ram group separation in feral

Seay sheep on llirta Island, Great Britain. In discussing bighorn

sheep and some other northern ungulates that have access to mountains,

Cowan (1974) stated they "evince acrophilia, which loads them to

remain at the liiglicst possible altitude on the winter range slopes.

This behavior is most strongly evinced by the males and in them is

one feature leading to a higher mortality rate." Such behavior would

explain the sex-group separation observed on the Thompson Falls winter

range.

Percentages of adult ram and ewe-juvenile group observations at

distances greater than 0.3 miles (483 m) from steep terrain were 22.2

and 8.9, respectively (Table 16). In contrast, mean distance to the

nearest 15— f oo t—m ininium (4.6 in) c .1 i f f w a s 50 feet (15.2 m ) and 132 feet

(40.2 m ) for adult ram and ewe-juvunile groups, respectively. These

re.sultt; may pnrtJ.illy r Lt f ] cc t th<' topograph ica I n.iturc of the study area

ratliLT than a dilference in selective bLihavior. I hti upi^cr elevational

ranges contain more small rock outcrops than l.ower elevation areas do.

Selection for tii g lier i; 1. ;v.i t i ons by ram g, rou ps might account loi the

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observed difference in mean distance to the nearest 15-foot-mlnimum

(4.6 in) cliff. Major steep terrain areas, however, appear to have

been equally available to all groups during the winter (Fig. 16).

j;lood (1963) reported that ewe-lamb groups selected winter

habitat with more readily available escape terrain than that selected

by rams. If distance to escape terrain at the moment of predator

attack is directly related to the probability of an individual bighorn

surviving the attack, lieavy predation pressure could have been a factor

in the development of an affinity for rough topography. If that was

the case, females might be expected to exhibit a higher development of

the trait since a greater affinity for cliffs would not only increase

their individual chances of survival, but would increase the survival

chances of their relatively vulnerable offspring.

The habitat use characteristics of young ram groups were nearly

identical to those of ewe-juvenile groups (Fig. 16 and Table 16).

Geist (1975) reported that young rams tend to increase the activity of

females by courting them throughout much of the year. lie stated that

any harvest programs should be designed to insure adequate older rams

in the population to draw young rams with them and away from the females

The limited number of observations of young ram groups during this

study tend to ccjnfirm that ram bands composed solely ol: sub-adult

( 3/4 curl) males will not occupy distinctly différent winter range

than ei,;e-i uveni le groups.

Habitat Use Ihilnt ed to barometri c Pressure and T'einncra Lure

There was a .significant (p = 0.05) variation in mean elevation and

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mean distance to the nearest 15-foot-minimum (4.6 m) cliff during

periods of low, medium, and high barometric pressure (Table 17),

Bighorns were observed at higher elevations and closer to cliffs

during periods of low barometric pressure. Mean elevation during

temperature inversion and non-inversion conditions was 3,640 feet

(1,109 m) and 3,402 feet (1,036 m ) , respectively. This was a signi­

ficant (p = .05) difference. Geist (1971) stated that mountain sheep

"appear to prefer the warmest elevations of the mountains, keeping

in the warm air above the thermocline."

An inspection of Fig. 17 reveals that low temperature extremes

during the study period were accompanied by medium to high barometric

pressures. During these low temperature extremes, it was warmer at

2,700 feet (823 m) elevation than at 4,300 feet (1,311 m). Temperature

inversion conditions during January and early February, indicated by

higher temperatures at higher elevations, were accompanied by low to

medium barometric pressures. A preference by wintering bighorn sheep

for the warmest temperatures available to them would account for high

utilization of lower elevations during high barometric pressure periods.

This type of behavior wouId also account for the increased use of higher

elevations during temperature inversions.

The low average distance to the nearest 15-foot-minimum (4.6 m)

cliff under low barometric pressure conditions is probably a reflection

of the physical characteristics of the winter range. Lower elevational

areas contain fewer small rock outcrops than higher elevations do. An

upward altitudinal movement toward higher temperatures during inversion

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conditions (which tended to be periods of low to medium barometric

pressure) would result in bighorn sheep groups being observed closer

to 15-foot-minimum (4.6 m) cliffs.

Mean group size exhibited significant (p = 0.05) variations

during periods of decreasing, relatively stable, and increasing

barometric pressures (Table 18). The highest mean group size occurred

during conditions of relatively stable barometric pressure and the

lowest during decreasing pressure conditions. Stelfox (1975) reported

a significant (p = 0.001) positive correlation (r = 0.256) between

barometric pressure and numbers of bighorn observed on open winter

ranges. This was interpreted as reflecting an abandonment of exposed

winter grasslands with the onset of lower barometric pressures

preceding winter storms. The reduction in mean group size during

periods of decreasing barometric pressure observed in this study may

reflect a tendency by bighorn sheep to seek shelter in anticipation of

a storm. Oldemeyer (1966) reported that bighorn sheep in Yellowstone

National Park often utilized small patches of conifers and deep ravines

as shelter. Such behavior during decreasing barometric pressures would

make bighorns less observable and might result in smaller observed

group sizes.

Bedding Site Characterization

The mildness of the 1975-76 winter in the Thompson Falls area

resulted in poor tracking conditions due to lack of snow cover. As a

result, only 189 bedding sites of known use periods could be located

(Table 19). The small sample size precludes definite conclusions

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about possible differences in characteristics of day and night bedding

sites. The data is suggestive, however, of a positive association

between night bedding sites and conifer cover. Beall (1974) reported

that elk selected night bedding sites with greater conifer density

as temperature decreased. Moen (1968) pointed out the energy conser­

vation advantages of bedding near conifers. Geist (1971) stated

"Wintering mountain sheep reduce waste of energy by avoiding excessive

heat loss and excessive energy expenditures in foraging and social

life. ..." The mean distance to the closest conifer and mean canopy

coverage characteristics of night bedding sites suggest that micro-

climatic conditions related to conifer cover may influence selection of

night bedding sites by bighorn sheep. The presence of conifers on the

winter range is probably not essential to winter survival since Spencer

(1943), Moser (1962), and Flook (1972) reported bighorn sheep wintering

above treeline. Further research into energy expenditure by wintering

bighorn sheep is necessary before the potential importance of conifer

cover on winter range can be evaluated.

Fecal pH

There was a significant (p = 0.05) difference in mean fecal pH

values for bighorn sheep (6.92) and mule deer (6.85) (fable 20).

However, the technique tailed to provide useful species differentiation

criteria due to the large amount of overlap in fecal pH values. In

contrast, Howard (1967), Nagy and Gilbert (1968), Howard and DeLorenzo

(1974), and Krausman et al. (1974) reported fecal pH to be a useful

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method for differentiating ruminant fecal pellets. The failure of

the fecal pH method to adequately differentiate between mule deer and

bighorn pellets on the Thompson Falls winter range underscores the

warning of Howard and DeLorenzo (1974): "We believe each area and

species ol interest sliou Id be studied carefully before applying the

technique in large management situations."

Food habits

Micrchistological analysis of fecal material indicated that the

winter diet consisted of approximately 38 percent grasses and sedges,

51 percent browse, and 11 percent forbs (Table 24). Bluebunch wheat­

grass had the highest percent relative density in the winter fecal

material, followed by mountain maple, servicebarry, Douglas-fir,

Ceonothus spp., bitterbrush, and yarrow in decreasing order. Food

habits studies from other bighorn sheep populations indicate that the

percentages of grasses and sedges, browse, and forbs in the winter diet

vary widely. Schallenberger (1965) reported that the bighorn winter

diets in the Sun River, Montana, area consisted of 36 percent grass,

43 percent browse, and 21 percent forbs. Blood (1963) reported that

British Columbia winter bighorn diets were comprised of 7 2 percent

grasses, 24 percent browse, and 4 percent forbs, with bluebunch wheat­

grass the most important forage species. Oldemeyer et al. (1971)

reported bighorn winter utilization percentages of 61.4, 21.5, and 17.2

for grasses and grasslike plants, shrubs, and forbs, respectively. Blue­

bunch wheatgrass was the main forage species.

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Bluebunch wheatgrass, mountain maple, and servicebarry accounted

for over 51 percent of the plant fragments in winter fecal material

from tne Thompson Falls study area. Management for the perpetuation

of these species on the winter range is recommended. The large

percentage of browse in the winter diet probably reflects the relative

scarcity of grasslands on the winter range. The high productivity

of the population indicates that a browse-dominated winter diet is

adequate. Demarchi (1968) reported yarrow to be high in crude fat

and crude protein in March on British Columbia bighorn sheep winter

ranges. The preference for yarrow over other forbs by the Thoraspson

Falls bighorn sheep is probably related to forage quality. Douglas-

fir accounted for over 8 percent of plant fragments in winter feces.

Simmons (1961), Moser (1962), and Capp (1967) reported conifers in

winter bighorn diets. The relatively large amount of Douglas-fir in

the diet of a healthy population under no apparent nutritional stress

may indicate that this particular conifer fulfills some nutritional

requirement. It is also possible that relatively high utilization of

more preferred forage species has resulted in the incorporation of less

preferred species into the diet.

Forage Utilization

Utilization, as measured by percentage of twigs browsed on lower

elevation areas, was 69, 78, 56, and 72 percent for serviceberry,

mountain maple, bitterbrush, and chokecherry, respectively (Table 25).

Bluebunch wheatgrass utilization at lower elevations was 30 percent

by weight. Utilization levels increased at higher elevations with at

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least 85 percent of the twigs browsed on all shrub species measured.

Bluebunch wheatgrass utilization was 55 percent by weight at higher

elevations. Oldemeyer et al. (1971) reported that utilization of

bluebunch wheatgrass in Yellowstone National Park exceeded 70 percent

on two winter ranges. Stelfox (1975) reported 58 percent grass

utilization on three heavily used ranges he considered overgrazed.

Increased forage utilization at higher elevations on the Thompson

Falls study area was probably due to the use of those areas year-long

by bighorn sheep. The upper elevation sampling areas between 3,800

and 5,000 feet (1,158 and 1,524 m) were used heavily by rams during

the 1975-1975 winter. Casual observations established that these same

areas were used by ewes and juveniles during late spring and summer

when bighorn sheep were very rarely seen at lower elevations.

The utilization transects were located in areas known to have

received moderate to heavy bighorn use and thus represent the heaviest

degrees of utilization on the study area. In addition, the degree of

forage utilization on a particular site within the winter range may

vary considerably from year to year.

During a severe winter, bighorn sheep would be expected to move

to shallower snow depths at lower elevations. Winter forage utilization

at lower elevations was not excessive during the study period, but

the quantity of available forage might not be adequate during a severe

winter. The ramifications of heavy utilization of preferred forage

species at higher elevations are unclear. Stelfox (1975) reported that

high forage utilization levels were correJated with low forage production.

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high lungworm counts, high winter weight loss, and low yearling:ewe

ratios. A more intensive investigation of forage utilization and

its relation to carrying capacity on tlie i'hompson Falls bighorn sheep

range is recommended.

Competition

live groups of mule deer were the only wild ungulates observed on

the winter range in addition to bighorn sheep. The Thompson Falls

bighorn sheep are not seriously affected by competition with other

native ungulates.

Fecal Group Counts Related to Site Factors

Observations of wintering ungulates with fecal pellets similar to

those of bighorn sheep totalled 19 mule deer. Total bighorn observa­

tions during the same period were 1,103. It was concluded that there

was no significant error in winter fecal group counts due to the

presence of fecal pellets not deposited by bighorn sheep. Moan fecal

groups per plot were 2.45, 1.00, and 0.68 for the ridge, upper slope,

and lower slope samples, respectively.

The high number of fecal groups on ridges was apparently the result

of frequent use of these areas as bedding sites. The highest concen­

trations of fecal groups on the study area occurred in heavily used

bedding areas. The positive correlation (r = 0.27) between fecal group

counts and elevation on ridges (Table 22) reflects the heavy use of

higher elevations in the sampling area by adult rams. I he correlations

of rabhitlrrusli (r = 0. 19), serviceberry (r = -0 .20), and evergreen

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ceonothus (r = 0.21) canopy coverages with fecal group counts on

ridges are difficult to explain (lable 23). If fecal group counts on

I idge.'-. wej e hif/hi'st in the vicinity of ma jor Loragc species in tiie

diet (iablc 24), the coirelations with serviceberry and evergreen

ceonothus would both be positive. This was not the case. In contrast

to lower and upper slopes, fecal group counts on ridges were not

positively correlated witli graminoid canopy cover. Fecal group

distrinution on ridges evidently reflects bedding site selection more

than feeding site selection.

Distance to the nearest 15-foot-minimum (4.6 m) cliff was

negatively correlated with fecal group counts on all three sampling

areas (Table 22). The group observation data, which established that

areas in close proximity to steep terrain were preferred by wintering

bighorn sheep (Table 13), indicated similar distribution of bighorns.

Distance to the nearest conifer was negatively correlated

(r = 0.22) with fecal group counts on lower slopes (Table 22). Sig­

nificant positive correlations existed between fecal group counts

and canopy coverages of total graminoids, bitterbrush, rabbitbrush,

and total slirubs (Table 23). Graminoid cover was positively cor­

related with canopy coverages of bitterbrush, rabbitbrush, and total

shrubs. Lower slopes were occupied primarily by the rockland and open

forest cover types with lesser amounts of shrubland-grassland. Sparsely

vegetated rubble fields are intermingled with open Douglas-fir-ponderosa

pine forests and small shrubl.and-grasslands containing bluebunch

wheatgrass and preferred browse r, jvc les. The ;;roup observation data

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revealed that open forest and shrubland-grassland cover types were

preferred by wintering bighorn sheep (Table 14). On lower slopes,

important forage species such as bluebunch wheatgrass (Table 24)

were associated with conifers. A selection for areas containing

preferred forage species would account for the observed pattern of

fecal group distribution on lower slopes.

On upper slopes, canopy coverages of total graminoids and ever­

green ceonothus were positively correlated (Table 23) and mockorange

canopy coverage was negatively correlated with fecal group counts.

Evergreen ceonothus canopy cover was negatively correlated (r‘- -0.15,

sig. = 0,15) with mockorange canopy cover. A preference for graminoids

and evergreen ceonothus as food items probably accounts in part for

pellet group distribution on upper slopes.

Management Implications

The Thompson Falls bighorn sheep exhibited a great deal of

selectivity in their use of available habitat during this study (Tables

9-15). This information suggests that habitat modification projects

designed to improve bighorn sheep winter range in the Thompson Falls

area should be concentrated on south and southwest aspects within 0.2

miles (322 m) of steep terrain ( > 80 percent slope). The principal

management objective should be the perpetuation of the shrubland-grass­

land and open forest cover types. These types received 85 percent of

bighorn winter use and contain far more bighorn winter forage than

rockland or closed forest cover types did (Tables 2 and 24).

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Other populations of bighorn sheep may not exhibit winter

habitat selection patterns identical to those of the Thompson Falls

population. However, the information from this study may be useful

in evaluating potential bighorn sheep transplant sites, particularly

if the transplant animals are taken from the Thompson Falls population.

Potential winter ranges should include grassland, shrubland, or open

forest cover types containing palatable forage within approximately

0.2 mile (322 m) of steep terrain. These open cover types should be

located on southerly aspects at lower elevations.

The potential climax plant community on a particular land unit

was not an important determinant of winter habitat selection by

bighorns on the Thompson Falls winter range (Table 15). Winter

distribution of sheep was related to the existing plant community

(plant cover type) (Table 14), which was often quite different

structurally and floristically from the potential climax community.

Once the plant cover types important to an animal species are

identified, the successional status of these communities becomes an

important management consideration. On the Thompson Falls study area,

many of the shrubland-grassland and open forest plant cover types on

southerly slopes at lower elevations occur on a DF/Syal/Syal habitat

type (Fig. 4). These areas have the potential to become closed forests

containing little bighorn forage. Because the sites are harsh, plant

succession is not progressing at a rapid rate. However, if the

maintenance of a large bighorn sheep population is the primary manage­

ment objective; on tliese lands, it may be necessary to reduce the conifer

canopy cover at some time in the future.

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Prescribed burning is probably the most desirable method of

reversing plant succession on bighorn ranges. Fire has been described

as important in creating desirable conditions on mountain sheep

ranges by Flook (1964), Geist (1971), and Stelfox (1971). Asherin

(1973) reported an increase in available production of mountain maple

and serviceberry after prescribed burning in northern Idaho. He also

reported higher use by wintering elk and white-tailed deer on burned

sites in comparison to control sites that were not burned. Vallentine

(1971) reported that several studies indicated bluebunch wheatgrass was

slightly damaged by fire. Conrad et al. (1966) determined that only

1 percent of bluebunch wheatgrass plants were dead 11 months after an

eastern Oregon fire. These findings indicate that fire is an important

factor on many ranges and would not be detrimental to the most important

forage species on the Thompson Falls winter range.

Fecal group counts provided a remarkably accurate index to the

relative distribution of bighorn sheep in relation to various habitat

factors (Table 22). Nearness to cliffy areas and high total graminoid

canopy cover were the habitat factors most consistently correlated with

high fecal group counts. The group observation data confirmed that

areas close to steep terrain and areas vegetated by the plant cover

types containing the highest coverages of total graminoids were

preferred by wintering bigtiorn sfiec.p (Tables 13 and 14) . The sampling

of fecal group distribution may provide a reasonably accurate, inexpen­

sive method of estimating relative habitat use by bighorn sheep on many

winter ranges.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110

Determining the proper carrying capacity of the Thompson Falls

bighorn sheep range is a complex problem. High forage utilization

levels at middle to high elevations may indicate the initial stages

of range deterioration (Table 25). However, without comparative data

from previous years, the significance of this Information is not

clear. The population is currently highly productive with heavy body

weights and low lungworm levels (Brown 1974). Rocky Mountain bighorn

sheep populations that reach high population levels are typically

reduced by a rapid dieoff. In discussing the bighorn sheep of the

Canadian Rockies, Stelfox (1971) stated "During pristine times bighorns

underwent sporadic fluctuations caused by severe winters, disease, and

changes in the condition of their ranges, influenced by weather, fire,

and interspecific competition." Buechner (1960) described these

reductions :

"If barriers such as restricted winter forage,

deep snow, and drought do not limit levels of popula­

tion, a point of high density is reached where disease

causes a sudden and severe mortality. The principal

disease involved is caused by lungworm. The triggering

mechanism seems to be poor nutrition from temporary

deterioration of forage on winter concentration areas . . .

The l u n g w o r m — pneumonia complex is unquestionably the

most significant disease in bighorn sheep."

Population reductions do occur that are not accompanied by a high

level of lungworm infection. Berwick (1968) and Matthews (1973)

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reported low lungworm levels in two declining western Montana bighorn

populations.

A massive dieoff may reduce the Thompson Falls population if it

continues to increase at the present rate. Stabilization of the

population at or below some unknown critical level would greatly

reduce this probability. If a stabilized population is chosen as a

management objective, more information on the carrying capacity of

the Thompson Falls range would be necessary.

To adequately assess the status of the Thompson Falls bighorn

sheep population in relation to carrying capacity, a long term

monitoring program is necessary. The collection of yearly data on

herd sex and age characteristics, lungworm loads, and forage utiliza­

tion levels would provide the minimum information necessary for

management decisions. I recommend that such a monitoring program be

initiated.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VI

SUMMARY

Winter habitat selection and use by bighorn sheep were inves­

tigated near Thompson Falls in northwestern Montana. The study area

was located in the southeast end of the Cabinet Range overlooking

the Clark Fork River. The precipitous terrain is characterized

by poorly developed soils and numerous talus cones emanating from

rugged crags of exposed bedrock. Intensive observations of wintering

sheep between 1 January and 30 March 197 6 provided data on herd sex

and age characteristics, group size, movements, home range, and habitat

selection. The relatively mild winter was characterized by moderate

temperatures and a lack of snow cover. Other data collecting

activities provided information on existing plant communities,

potential climax plant communities, fecal group distribution, fecal pH,

bighorn winter food habits, and estimated average percent utilization

of five major forage species.

Mean group size of 197 bighorn sheep groups observed during the

winter was 5.6. The mean size of adult ram groups was higher than

that of e w e — juvenile or young ram groups. Lamb.ewe and yearling.ewe

ratios were 92:100 and 42:100, respectively. Mean standard diameters

for adult females and adult males were 2.63 miles (4.23 km) and 1.89

I 1 2

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miles (3.04 km), respectively. Mean minimum home range sizes were

320 acres (129.5 ha) and 271 acres (109.6 ha) for adult females and

adult males, respectively.

Proportions of group observations within individual categories

of elevation, topographic position, slope steepness, aspect, distance

from steep terrain, plant cover type, and habitat type were compared

with the proportion of occurrence of those categories within the study

area. Results indicated an avoidance of elevations above 4,800 feet

(1,463 m), drainage bottoms and upper slopes, areas with a slope

steepness of 10-35 percent, east and southeast aspects, areas greater

than 0.2 miles (322 m) from steep terrain, closed forests, and the

Douglas-fir/ninebark habitat type. Preferences were shown for cliffs,

areas with a slope steepness greater than 80 percent, south aspects,

areas within 0.2 miles (322 m) of steep terrain, shrubland-grassland

and open forest, and the rockland-scree habitat type classification.

Measurements taken at a small number of bedding sites indicated that

bighorn sheep night bedding sites may be associated with conifers.

Adult ram groups were observed at significantly higher elevations

than ewe—juvenile or young ram groups. In general, the winter habitat

selected by young ram groups was similar to that selected by ewe-juvenile

groups. Bighorns apparently sought out comparatively warmer elevations

during the winter. Mean group size was lowest during periods of

decreasing barometric pressure.

The winter diet of bighorns, as estimated by microhistological

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114

examination of feces, was 38 percent grasses and sedges, 51 percent

browse, and 11 percent forbs. Bluebunch wheatgrass, mountain maple,

serviceberry , and Douglas—fir had the highest percent relative

densities in fecal material, in decreasing order. Percentages of twigs

browsed on four major forage species exceeded 55 and 84 percent below

and above 3,800 feet (1,158 m ) , respectively. Bluebunch wheatgrass

utilization by weight was 30 and 55 percent at lower and higher eleva­

tions, respectively.

Measurement of fecal pH values of bighorn sheep and mule deer

failed to provide a useful means of pellet group identification by

species. High fecal group counts were most consistently correlated

with low distances to the nearest cliff and high total graminoid

canopy coverages. The relative use of habitats by bighorn sheep as

estimated by fecal group counts was generally similar to that indicated

by direct observations of wintering animals.

The perpetuation of shrubland-grassland and open forest cover

types on the winter range by prescribed burning was recommended when

canopy coverages warranted conifer removal.

A long-term monitoring program to assess the status of the

Thompson Falls population in relation to carrying capacity was recom­

mended. This program would involve the systematic collection of data

on sex and age characteristics, lungworm loads, and forage utilization

levels.

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